video tutorial on how to control the shutter/aperture/gain [Archive]

bluegrass

2007 May 5th, 20:57

Okay, it's now on hv20.info:
http://hv20.info/yopu/hv20aperturecontrol.mov

I think worth a watch for ANYONE with a HV20!

You guys are so for advanced in your camera/camcorder knowledge. I take it this manipulation of the shutter speed & aperature on the HV20 wasn't expected from the typical person purchasing this camera, or it would have been designed to be a little bit more straight forward and easier to do.

I finally got in a nice comforatable position last night and dug into the HV20 book. I find the explanations & illustrations on how to do things with this camcorder very hard to follow & I'm a technical person. Is it just me, or are others finding the book to be hard to follow. This is my third Canon camcorder & I believe the others were the same way. I'm a guy and tend to wing it when possible and only go to the book when I can't figure something out. Hope someone brings out a HV20 for Dummies book.

Since I'm obviously from "RioLinda" when it comes to cameras, could you tell me what an ND filter is and also give an example of where you might want to make the effort to manipulate the appeture/shutter settings as illustrated in this video so you could improve your recording. I realize that is a real general question & maybe I'm a bit out of line asking, but could you give an example where point and shoot with this camcorder wouldn't give you very good results unless you went through some of the changes illustrated in this video. I think I know enough to know that you want faster shutter speeds for shooting fast motion and the lower the aperture number the wider the lens is open and thus lets in more light. The aperture also plays a part in the depth of focus or field. There, that reveals how dumb I am. I'm like my computer clients, it's a tool to get a job done. Of course the tool can be a lot of fun but when you don't know how to drive it, it can drive you up the wall.

duzzit_madder

2007 May 6th, 02:34

I like to think that no question is out of line. I've been on boards where peeps will flame newbs hard for stupid stuff but I hope this doesn't happen here.

So the only bad question is the one that you don't ask.

ND is short for Neutral Density. And all that means is it lets in less light. It won't change the color or saturation, just how much. You use ND filters to cut sunshine glare, the blue haze when you shoot landscapes, and when your scene is over exposed. ND filters come in different gradients so you can control how much light you want. If you go to Tiffen's web site (http://www.tiffen.com/tiffen_filters.html), they have all their filters listed and what they do and a very general how and why you'd use them.

As for how and why you'd want to mess with your settings, they teach whole classes on this stuff and it's way out of the scope of anything I'd post in one sitting. My advice would be to search wikipedia for 'aperture', 'shutter speed', 'depth of field', and 'gain'. How they all work together is something most people call, photography 101.

David

2007 May 6th, 05:27

this is a tutorial i made a few days ago on how to control the aperture and gain on the HV20.

That is a really really great demonstration of exactly how this little camera works and how to avoid the gain-up. Well done, Patrick. :hv20-smilie07: :hv20-smilie77:

Mal

2007 May 6th, 09:14

You guys are so for advanced....

duzzit_madder said it well; the reason for this forum existing, is so we may learn from each other. No one should feel they are soooo clever that no more can be learned, and no one should feel inferior thinking they shouldn't ask a question that might seem "too obvious".
[So far] the members of this forum are absolutely amazing in their willingness to share and help. Brings a tear to my eye! :hv20-smilie108: No, really.

Anyway, with that out of the way, I just wanted to mention that the Hv20 is one heck of piece of equipment. I'm equally baffled by its capabilities, and naturally the manual seems a daunting task to follow. Look at all this little video cam can do.....oh, and then you got the still capability of it also.
It will take some time to get used to it. All I can suggest is to learn by shooting stuff. Use AUTO if it makes you feel more comfortable and allows you to concentrate more on the content you're shooting. After a while I bet you'll start to explore the manual settings, and find the cam is quite a capable instrument, even if not necessarily designed for anything other than a "holiday cam".

:hv20-smilie110:

24Peter

2007 May 6th, 11:19

In addition to logging into this forum daily, Mal's best suggestion is to learn by doing. Read the forums and manual (yes Canon has a particular style to its manuals which I think can be pretty challenging), but then go out and shoot with a bunch of different settings so you can see the acutal results. Also - did you know that if you plug your camera into a TV (HDMI or component) in camera mode, you can see all your changes live and immediately compare what one setting looks like vs. another?

Also - on the ND thing, we suspect there is (electronic?) ND filtering already built in to the HV20. Buying additional external ND filters is probably only necessary if you shoot under brightly lit conditions like snow or sand/water, or if for artistic/technical reasons you want the apeture wide open while shooting outside. I used my HV20 recently outside in the midday desert sun and sand in Palm Springs California and the camera had no problem properly exposing the scene without any add-ons.

bluegrass

2007 May 6th, 13:50

duzzit_madder said it well; the reason for this forum existing, is so we may learn from each other. No one should feel they are soooo clever that no more can be learned, and no one should feel inferior thinking they shouldn't ask a question that might seem "too obvious".
[So far] the members of this forum are absolutely amazing in their willingness to share and help. Brings a tear to my eye! :hv20-smilie108: No, really.

:hv20-smilie110:

Mal, now I almost got a tear in my eye. I'm thankful that so for all the people here seem to feel the way you feel about it. There appears to be a great diverstiy of people using this forum which makes it really cool. My philosophy has to always keep and open mind and keep on learning. I'll keep on shooting videos and learn as I go. I'm not at all against tweaking and moving out of the "Auto" mode when I can & it will pay royalties. I was just getting a little anxious about the ability to make adjustments as fast as necessary while shooting. Ninety percent of my shooting is outdoors of musicians on a well lit daytime stage or a well lit night time stage plus shooting camp jams in fairly low light. The last one is my big concern. I'll do a lot of testing at home in the evening in the back yard to see what I can come up with as the best camera to use the best way to shoot. Sometimes I'm actually shooting around a campfire and the fire is the only light while other times I might be under a canop;y alongside a trailer and there are a few lights. If the HV20 doesn't hold up well to poor light conditions, I can always move back to my older Canon's - Elura 65 & 100. Actually I have found that a little bit of graininess actually isnt' that bad when your watching a campfire jam. It kind of adds to the ambience. So at times, you can let a technical deficiency become a positvie thing.

Say Mal, just one thought I had about the forum. As there become more and more posts that have great solutions in either a step by step or a videos such as Davids, they wind up getting hard to go back an put your finger on them. Do you think where there appears to be a good solution to a problem, they might either be duplicated or moved to a "Solution" thread. I know it would require you objectively determining which ones would warrent being placed into this special thread but I thought you might consder it. They may have to be put into a few categories as the number of solutions get posted. I know from experience with my own website, it gets more and more difficult to organize and implement something like this after the site grows and this forum seems to be growing very rapidly. If it isn't already, this place is going to be the premier website to go to for information about consumer HDV and the Canon DV20 specifically.

I know it's always been a delima in this information age we live in, to quickly put your hands on the information you want. But when you can, it's a wonderful thing.

Michael Hackney

2007 May 6th, 16:53

Great tutorial! I got a question answered that I was thinking about for a while.
Thanks a million!

Patrick Jennings

2007 May 6th, 18:54

YAY I got sticky status! I'm glad you all found it helpful :)

Mal

2007 May 6th, 18:56

YAY I got sticky status! I'm glad you all found it helpful :)

:hv20-smilie77: You bet!!

bluegrass

2007 May 8th, 23:14

Sorry to post here but I hunted all over for the clip & couldn't find it. I had downloaded and saved the clip on my desktop so I could go through it at my leisure. I just finally made it all the way through changing all the setting as he did on the tutorial clip. I did stumble on a couple things and this might help someone else from the problems I had. You do need to set up to shoot stills & you also have to be in manual focus for some reason. I don't believe he mentioned this on the clip although I have a little difficulty with his British accent or forgive me if it's an Austrailian accent.

Anyway, now that I've figured out how to do it the only way to change the aperture is via changing the exposure number. They seem to be tied together. My question is if they are tied together why not just adjust the exposure number. I'll look again in Wikipedia aren't they the same thing? I know exposure is the measurement of the amount of light hitting the film or in this case the sensor. It is controlled by the shutter speed and the aperture. The HV20 seems to have an exposere number from 0 to -11. At any given shutter speed my contention is 0 represents a wide open shutter which appears to be f1.8 and -11 represents the aperature closed down to I believe f4.6 or something like that.

Since I assume that the aperture & exposure numbers are being controlled manually in this clip, I didn't get the point of pointing the camera a light at one point in the clip. What the heck was that all about. I also thought I understood him to be using decibal as a measurment of gain. Maybe I misheard him but I associate decibles with audio level not photography.

Mal - sorry I couldn't find the proper place to post this. Feel free to move it over to the right place. I feel like I have accomplished something pretty cool for pretty much of a novice when it comes to this stuff. I'm not sure yet how I'll use it and like I said that one step using exposure number changes to change the aperture the way he went about it just didn't make any sense to me. Maybe when I actually do some shooting using his method, it will start to clear up & make more sense.

Mal

2007 May 9th, 05:38

Hey bluegrass,
yeah, I have to concede that Patrick's tutorial is for something that gets quite complicated. Which is why the tutorial is so cool and helpful.
The main goal is to try and stop the HV20 from adding GAIN (and to be able to control aperture). The HV20 wants to both these things by itself. Basically, Patrick's tutorial is meant to FORCE the HV20 NOT to use gain, and to be able to select aperture. Gain = bad, as it will simply boost video noise. Electronic gain will just make everything brighter, which seems okay, but it is also making the video noise brighter. And that's not ideal.

So Patrick's tutorial shows how to stop the HV20 from adding gain automatically, but instead TELLING the HV20 what to do. The pointing-the-cam-at-a-light is a MUST-step in this process, by the way.

Its purpose is to squeeze the maximum picture quality out of the HV20; and as with every camera that is almost always achieved with MANUAL control.
Maybe some day the HV20 will have a firmware upgrade to make this easier, but considering that it is an inexpensive [relative to its picture quality] little camcorder, this may never happen.

Hope this explanation helps; it's early, and I still need my second cup of coffee, so it might not make much sense... :)

bluegrass

2007 May 9th, 10:04

Mal - Before you banish me to the Wikipedia room, I was just there trying to get a good explanation of how digital cameras and camcorders change gain & how gain is explained for a digital camcorder. I didn't find any explanation. If someone else finds a room on the Internet that does, please post it for us. I think maybe I'm correct in thinking that digital gain is pretty much the equivilent of film speed. You can increase the film speed to a high number to deal with light conditions & maybe high shutter speeds, but it can cause graininess in the resulting picture.

Let's relate a real life situation with our HV20. We are shooting inside our home. The scene is of the our first born taking her first steps. Just typical lighting, maybe the scene moves into the hall and it gets less light. On automatic, the camcorder decides what shutter speed and aperature to set. It may cut down the speed to compensate for the low light which might cause some blur as you little girl starts walking. It might also open up the aperture to a f4 or something bigger than the f1.8. Now the resulting clip may have a little blur & some grain.

If we took over the shutter & aperture settings manually as in the tutorial (lets assume that we had a little time to prepare for this event). How do you think we could improve what the camcorder was trying to do when it was in the automatic mode. Please, I'm not trying to be a wise guy here, I'm really trying to learn. If there are some secrets this camera holds that will allow us to take more professional footage, lets keep shining a light on them.

In the meantime, I hope everyone is having a good time with this great camcorder. I have a feeling that everybody that pays attention to the posts here are going to become pretty knowlegeable users of the HV20. Every little bit of contribution helps. Even you Mal, who seems to be pretty knowegeable, has remarked that you learned something new from someones post.

My little way of getting back to some good information I have found is to filter all the posts until you can build a nice scrapbook of info. There are many approaches on how to store the info we run across on this forum and the Internet. Since I gather info both at home and at work, whenever I run into something I think will be useful, I go to the browser file pulldown menu and use the "send link by email" and email it to my home email address. I have a folder in my email client I have named "technical". All of these email get put into that folder. I will at least have a trail that will get me back to the info. The next step would be to copy and paste the real text to a database of some sort. Ain't the Internet great?

David

2007 May 10th, 02:21

I think maybe I'm correct in thinking that digital gain is pretty much the equivilent of film speed. You can increase the film speed to a high number to deal with light conditions & maybe high shutter speeds, but it can cause graininess in the resulting picture.

That's a pretty accurate analogy. Gain is effectively making the sensor more sensitive to light in the same way that a faster film speed would. The downside, in both cases, is that you sacrifice image quality.

If we took over the shutter & aperture settings manually as in the tutorial (lets assume that we had a little time to prepare for this event). How do you think we could improve what the camcorder was trying to do when it was in the automatic mode.

By setting the shutter and aperture manually in the way the tutorial demonstrates, you're setting up the camera to avoid the addition of 'gain' and therefore you are inherently improving the image. You're making a decision about shutter speed, aperture and overall exposure and you're locking in these settings. That being said, you won't necessarily be able to shoot in any random situation you might happen upon.

In your example of walking from one room to the next, there simply might not be enough light to get an acceptably bright image when you've locked your shutter speed and f-stop at whatever it's been locked to. In that case, you'll either need to adjust your shutter speed, or open up your aperture. If you can't do either (because you're already shooting wide open and you're at the slowest acceptable shutter speed available) then your only option is to either live with an underexposed image or unlock things and allow the camera to add gain.

bluegrass

2007 May 10th, 10:05

That's a pretty accurate analogy. Gain is effectively making the sensor more sensitive to light in the same way that a faster film speed would. The downside, in both cases, is that you sacrifice image quality.

The thing I don't understand is the sensors can't be made more sensitive, short of increasing the voltage or something, so what is happening in the digital camera/camcorder world to equivalize the film speed without touching the shutter/aperture?

I would think wide open aperture and the slowest shutter you can set would be about all you can do. Is the shutter speed acting on every frame? If shutter is 1/30s and frame rate is 30fps would that mean the shutter is effectively closing once for each frame. I'm sorry, it's just in my nature, to try and understand what is really going on after I press that little red record button. I know these are just little pieces of what makes up the process of capturing a piece of video. If others wouldn't be interested in traversing this area of recording, than we can drop it & I can continue my research outside of this forum.

There is so much to learn and figure out - reverse cinecline, pull-down, and many many more.

David

2007 May 10th, 13:26

The thing I don't understand is the sensors can't be made more sensitive, short of increasing the voltage or something

You got it. Gain in video is the same idea as gain in audio.
"The increase in signaling power as an audio signal is boosted by an electronic device. It is measured in decibels."

Gain (in dB) = 20 x LOG(Voltage Out / Voltage In)

rsovitzky

2007 May 13th, 15:31

Patrick,

You started mentioning dB values of gain toward the end of your video. Where did you get those numbers from?

Rick

Patrick Jennings

2007 May 13th, 20:51

Rick,
every exposure dial notch above wide open f1.8, is adding 1.5db of gain.
i originally got the values from a thread at dvinfo.net, but it wasn't confirmed. then barry green over at dvxuser.com confirmed them.

guru

2007 May 14th, 21:15

bluegrass

2007 May 14th, 22:35

bluegrass, gain in video is the same thing as ASA in film, or ISO in digital photography. So basically, when you (or camera) add gain, it means more voltage on the senzor, and thus more noise, exactly as in digital cameras. So thats why you want to control your gain, and this tutorial shows how to prevent the camera to do it automatically.

You know, I've been shooting quite a bit of video in the past couple years are so at night, around a campfire or next to a camper without much light. I always wondered why the footage got real grainy. Now I know that it's the camera saying that their isn't enough juice coming from those sensor so let crank up the votage on the cathode.

At anyrate, I guess without a very high end camcorder, it's either no video or some video with some grain. Although now, thanks to some things I've learned right here on this forum, I know a few tricks to try around the campfire this weekend. I'm thinking that since the most motion I'll be taping will be the arm stumming a guitar or a mandolin so why not lower the shutter speed to around 60 or lower and maybe I can than lower the gain (exposure) a little. Or do you think I should try increasing the fstop. Whatever I do, I should avoid pushing that exp up, right?

While I'm here posting, anyone care to give a simple explanation of what gama is. I know I like to play around with gama on my photos in Microsoft Photo editor to brighten the colors a little but I never new what the heck I was doin' besides making it look better to me.

guru

2007 May 16th, 12:40

bluegrass

2007 May 16th, 13:53

You should use 24p, it's the best for low light, and try to lower the shutter as much as you can for that situation (if it's possible in 24p), and use your widest zoom setting, to have wide open aperture (F1.8), so more light on the sensor.

Hey Guru, thanks for the tips. I'm thinking of throwing my 32'' monitor in the car to have on hand just to check how the video looks playing back from tape. Will the 24P tape that I capture play back at 24P via the HDMI. Do you know whether I will see any representation of the 24P mode playing back from the camera. I just hate to shoot a bunch of 24P without being able to play some of it right back to see if it's looking OK. I figure it might be difficult to make an intelligent decision of whether it's doing OK by just watching the on board LCD as I tape. I'm sure if I set a 32' monitor on a table near the campfire as a jam is goin' down, that would go over like a lead balloon. Hey, maybe I'll get some folks to just do a little campfire jam tomorrow night, just as a test to see how 24P looks on the playback.

Chimpunk12

2007 May 19th, 19:55

The thing I don't understand is the sensors can't be made more sensitive, short of increasing the voltage or something, so what is happening in the digital camera/camcorder world to equivalize the film speed without touching the shutter/aperture?

Video gain on the HV20 works the same way as AGC (automatic gain control) works on an audio recorder. But normalizing the topmost value to white also brings up the noise floor.

BTW, there is a way to disable the AGC. Hint: the camera is then limited to daylight white balance.

sean90291

2007 May 28th, 11:10

After going through the process described to control automatic gain and lock shutter speed, will the camera remember these settings when you turn it off, take out the battery, and later turn it on again? Or will you have to re-do the set-up each time the camera is powered down.

crobs808

2007 May 31st, 15:57

You guys are so for advanced in your camera/camcorder knowledge....Of course the tool can be a lot of fun but when you don't know how to drive it, it can drive you up the wall.

there's not too much to figure out on the hv20...it is small, very few features, and little to no manual controls. i mean there isn't even a "M" setting, just program mode only. other than shutter/aperture, which have been around since the early 1900s, there isn't really anything new.

just remember this..on the hv20, the higher the shutter, the darker/crisper the image, the lower, the more motion blur and lighter...the higher the aperture the darker, the lower the aperture the lighter.

that's pretty much it for the hv20..you dont have gain controls, or ae shift, or xlr audio inputs, or anything else that is on professional cameras. i mean i love my hv20, but it's like the "AOL" of the HD camera world. dumbed down, stipped, and very little felxibility. there's a reason it's only $1,000..i was really excited when i got it...then after a few hours felt like a cheap plastic toy next to what i've been used to (solid metal, hard rubberized bodies and zoom ring controls, 20x lenses and canon L glass using EF lenses...but the hv20 is good for non-critical filming)

sfdex

2007 June 12th, 20:07

Hey, all --

This is a fascinating thread; I've been thinking about an HV 20 but had been avoiding it because my understanding had been that it wasn't possible to lock the gain out of function, so Patrick, thanks very much for this.

I don't have an HV20 yet, but do have some background in videography (it's my profession). So, here are some comments inspired by this thread.

Gain: as said before, it's electronic enhancing of a too-dark image. It's measured in dB (decibells) just like audio is measured, because it's a signal strength measurement, not specifically an audio or light level measurement. Perhaps a better analogy of the gain might be in Photoshop (or whatever photo-editing software you prefer) when you use the brightness-contrast control to brighten a photo that's too dark. Sure, you can brighten it, but when you do, all sorts of grain and noise shows in the image.

Shutter (speed): is the amount of time the sensor is exposed to light. It's measured in fractions of a second (or in some cases in full seconds, though I don't know if the HV20 can have multiple-second shutter speeds). The longer the sensor is exposed to light, the brighter the image registers on the sensor. Of course, the longer the sensor is exposed to the light, the more opportunity you have for motion-blur -- that is your subject can move while the shutter is open. If you're shooting at 30 frames per second (which is more or less equivalent to 60i), you can shoot as slowly as a thirtieth of a second per frame and still have normal looking motion. If you're shooting at 24 frames per second, the camera can keep its shutter open for a 24th of a second, or nearly 30% longer, and therefore can capture images in slightly lower light conditions. If the camera can shoot at, say, 1/12 of a second, it will keep the shutter open for 1/12 of a second and send the same image to two frames (at 24fps). This will result in somewhat choppy motion, but will allow you to shoot in half as much light. Depending on the subject, it might work.

Aperture: This is the diameter of the opening through which the light travels to the image sensor. Aperture is measured in f-stops. (F-stops are calculated as the ratio of the size of the opening to the focal length of the lens; interesting but not entirely necessary to know.) The important thing to know is that the smaller the f-stop number, the larger the opening. And the larger the opening, the more light can pass through the lens to the image sensor. A physical property of lenses is that the smaller the opening (higher the f-stop number) the greater the "depth of field" of an image -- that is, the longer range of distance that objects will be in focus.

So, if you have a tape measure on the floor running lengthwise away from you and you point a camera at it, you'll see that a particular distance is in focus. Let's say that you're shooting at f-5.6 at a shutter speed of 1/60 of a second. You look at the image and see that the 3 foot mark is crystal clear, but the 2'10" mark is a little "soft" and the 3'4" mark is a little soft. If you open up the aperture (say to f-4), you'll be letting more light in, so to keep the exposure the same, you'll need to change the shutter speed to 1/120 of a second. Because the aperture (f-stop) is larger now (smaller number), the depth of field is "shallower", so all that will be in focus is from 2'11" to 3'1". But let's say you want more of the tape measure in focus. So, you change the aperture to f-8. To keep the exposure the same, you'll need to change the shutter speed to 1/30 of a second. But at f-8, you will see that the focus will be clear from 2'8 to 3'8.

This is why it's important to have control of aperture and shutter speed. Patrick's tutorial shows how to take complete control of the exposure in your camera, which is really important if you want that much control of the image.

But for most hobby applications (and a number of professional ones), the automatic settings are just fine. They'll help you get a clear, properly exposed image to the best of the camera's ability. So, for your child's first steps, by all means, use the automatic. Under most circumstances, it'll look great!

That's probably a LOT more info than anyone was asking for, but hey, I used to teach TV production, so it's hard for me to resist!

I'll keep reading this forum and very likely will be buying an HV20 soon.

Thanks for all the great info here!

- Dex

Ian-T

2007 June 12th, 20:46

Dang Dex!!! Thanks!

sean90291

2007 June 13th, 10:35

Awesome information. A tutorial like that makes me fall in love with the Internet all over again.

I don't have an HV20 yet. I'm curious if once you lock your exposure whether all three variables (gain, shutter, aperture) remain unchanged, no matter what the lighting conditions. That's what you seem to be saying. I hope so. :-)

bluespoet

2007 June 14th, 12:41

I use wireless cell phone connection for my laptop and it is slower than slow
so I cannot download the video, but a written tutorial would go a long way to help me benefit from this thread and I am sure others like me

VaNdaL

2007 June 15th, 08:46

CJDaniels

2007 June 20th, 01:19

I'm slightly perplexed... Okay so if you use this method for low light, there's no gain at 0 setting (for example) and the Aperture is at its widest F1.8, then every notch up from 0 is adding gain but stays at lowest Aperture of F1.8, and with every notch down will increase aperture but make things darker, right? At 0 setting everything is way way darker than auto settings (cause of no added gain) and to get it to match the brightness of the auto settings with the exposure locked method you need to lower shutter speeds to lower than 1/25 resulting in blurred/stutter effect, I can't see how this helps shooting in low light conditions, HELP!!!

Okay so I just tried something a bit different, I didn't point directly at a light source before I locked exposure, just nearby the light, this helped with getting a satisfactory shutter speed to brightness ratio without getting jerky footage, but I have yet to see the recorded results on my pc.

Think of it this way. 1.8 is the smallest number but the biggest apeture opening. It can get no bigger. Gain is an artificial way of making your image brighter. For those who are into video whether it be a professional or a in-the-know ameture, gain is not a pretty thing. Grainy and fuzzy (which may work for some effects, but generally not.)

So that being said. This tutorial is teaching you how to control your gain, not control the amount of light reaching the sensor. What you are doing is preventing gain from kicking in, doesn't mean you will have enough light for the shot, just a way of preventing the grainy effect of gain. This technique shows you the highest level of light w/o gain. Or if you allow some gain, for you to know exactly how much gain you are adding... i.e. 1.5....

So it is a trade off, maybe the scene may be a little darker than you like at F1.8, but you have let the most possible light in, without letting the gain kick in.

Pointing at a less bright light is not going to change when the gain sets in, it just is going to give you an inaccurate reading as to when it actually does. What matters is if you are happy with the final results, not necessarily if the techniques works for you or not.

VaNdaL

2007 June 20th, 07:09

CJDaniels

2007 June 21st, 16:44

Thanks for the explanation, it's good to know that you can control how much gain is applied, though I now seemed to be hampered by the pal version as I can't check the aperture in Tv or Cine mode without changing to SD Card mode and loosing the exposure lock.

I had that issue also and I fixed it by...... I can't remember... It has something to do with the menu settings though,..... Dang

VaNdaL

2007 June 23rd, 00:29

I had that issue also and I fixed it by...... I can't remember... It has something to do with the menu settings though,..... Dang

I got it now, need to go to still rec in menu (tape mode).

sean90291

2007 June 23rd, 02:30

When you lock your aperture at the widest setting 1.8, and then zoom in and it shows 2.4, you're still at 1.8 in actuality right? It's just the bug in the HV20. But my real question is, if you lock your aperture with the lens cap on in Cine mode, the camera will lock off at the widest setting (because it sees only darkness). Zoomed right in, this reads as 2.4. However, is this in fact 1.8?

Patrick Jennings

2007 June 23rd, 10:54

no the glitch is if you're zoomed in at 7x and it shows f/2.8 or something.... then you lock, when fully zoomed out it shows 2.0 instead of 1.8.... the more you zoom in, the smaller the aperture.. here is a table
zoom/aperture
0 1.8
1 1.92
2 2.04
3 2.16
4 2.28
5 2.4
6 2.52
7 2.64
8 2.76
9 2.88
10 3

it should be f/3 zoomed right in, but if it showes f/2.4 like you say then i could be wrong.... i havn't tested this and i can't right now coz i'm at work... i'll get back to you

sfdex

2007 June 24th, 02:36

This may not be a glitch, though, not having an HV20 I can't verify it.

However, the long (telephoto) end of all lenses will be "slower" or have a higher aperture number than the short (wide) end. It's simply a factor of how the glass moves around in the lens to magnify the image.

Then again, it may be a glitch. Just thought I'd throw some more general photography info out there!

- Dex

Appleidiot

2007 June 24th, 15:54

One thing I noticed, which is completely off the subject...but, the mechanism noise at the first being picked up by the mic...then, boom noise gone. The only reason I bring this up is because I noticed mine to be quite noisly and it never goes away. Just curious.

sean90291

2007 June 24th, 20:10

CJDaniels

2007 June 25th, 02:11

No, most all zoom lenses have a Fstop range, that is why on a still lens fstops are listed like 2.8-4 Meaning that at it's widest angle it is 2.8 but at it's closest zoom it is F4.0

tkmslee

2007 June 27th, 12:50

How is it that you know you are at 0db of gain when you aim it at the light and lock the exposure?

Also, is there an effective way of adjusting aperture and shutter speed from one lighting situation to the next?

My main concern is that I always want the gain at 0db, and can you use cine mode and still have control over the shutter and aperture?

FreddieZ

2007 July 2nd, 09:05

Here's a TEXT link I found right here on HV20.com, but points to DVXUser's HV20 forum.

http://www.dvxuser.com/V6/showthread.php?t=96502

Open the "full article" link and enjoy...

http://dvxuser.com/jason/hv20/

eugenehug

2007 July 2nd, 20:47

Man..
I could have used this info before this weekend. I was shooting on my crappy Killer Klown movie and I lost a scene that was shot on auto mode, it looked WONDERFUL ( you can only imagine HOW WONDERFUL !! ) in the LCD, the scene was shot in diffuse, indirect light. It was cloudy outside too !! The scene was that of the glamour model, Liz Ashley in the nude !! She has extremely fair complexion and all the good bits were blown out !!!! I am soo angry, I could bite myself. I now know NOT to trust the LCD !!

Images deleted. They were neither taken with the HV20 nor did they add any useful information to this thread. - Worley

steveHV20

2007 July 14th, 04:26

Hi, just joined forum today. I can not correctly view the mov file, my Quicktime says software not available on server, anny suiggestions?
thanks

HCoremark

2007 July 16th, 21:53

To summarize:
In any give lighting situation, with a fixed shutter speed, you can only alter the light hitting the sensor by changing the aperture? So allowing the HV20 to go beyond that wide open aperture by adding gain you are merely artificially brightening the image and not adding more detail.

In darker lighting conditions would everyone who knows about such things prefer to try and brighten an image later in post that trust the camera to improve things with gain?

raeshao

2007 July 17th, 00:47

In darker lighting conditions would everyone who knows about such things prefer to try and brighten an image later in post that trust the camera to improve things with gain?

Hello, new HV20 user here. After seeing dark footage with and without gain noise, I'd definitely choose to lighten non-gained images after the fact. Although it depends on how dark your footage actually is, and what you're actually looking to do. For home movies, a little gain to boost dark images is surely acceptable. If you're looking for the best image quality possible from this little cam, you're going to have to control things as much as possible while shooting, as well as bringing the footage into post.

I just watched the video, and read the written how to from dvxuser.com. There seem to be a couple of discrepancies. The main one is that Barry Green was recommending the use of CINE mode over a straight shutter priority mode (Tv). Flipping back and forth, it looks like one would be able to get a few more usable settings (-11 to +11 in a certain instance, more on that in a sec) using the cell phone hack in CINE mode. The trick certainly works in Tv mode, but after +6 or +7, things kinda fall apart here. Using my Nokia 6131, I am able to get usable settings @ 1/48 from -11 to +9 in CINE mode.

While playing around, I noticed that if I turned on the camera light while doing the cell phone trick, I was able to get the setting range to top out at +11 (f1.8 @ 1/48). It's cool and all, but I still have to get out and shoot some actual footage. For reference, I was getting f4.0 @ 0 with just the phone, and f4.8 @ 0 with the phone and the light. This is right where you want to be to get things wide open with the correct shutter speed at +11.

I've also found that using too bright of a light won't let you get into an acceptable range. The image stays really dark throughout the entire range. Which makes sense. It's nice to see so many trying to squeeze all they can out of this camera.

-r

seider

2007 July 24th, 01:58

this thread has helped me out soo much (even thou i dont own a hv20 yet:hv20-smilie119:) but i would like to know a few things and if its not the right place to ask them could you just tell me and i will re post elce-ware. ok...
1. for filming snow should i use polerized filter
2. filing snow and filming fast moving objects (skiiers) should i keep my shutter speed at 1/50th.
3. in the tutorial, after he pointed camera to the light and locked exposure the image was soo dark, is that how he was meant to leave it, what was he ment to do next, pump up exposure
4. does EXP stand for exposure

thanks to all the previous questions and answers because they helped me out soo much, i hope the answers to my questions help others out.

and its nice to see a forum with such nice people out there willing to help out others.

Rumpelgeist

2007 July 30th, 20:22

This article discusses the same topic, that is, manually controlling exposure of a Canon camcorder.

http://www.elurauser.com/articles/manual_mode.jsp

The article is largely about Elura 100, not HV20. But the principles are the same for all Canon consumer camcorders.

altero

2007 July 31st, 10:20

Anx

2007 July 31st, 14:10

I didn't notice this mentioned on here, but I use a slightly different approach that was outlined off of the Brevis35 owners group. They reference this thread and video at the start, and at least with the 35mm adapter I like the results:

1. All the basic steps are the same, with the exception that you turn on 70% zebra in the settings section
2. Set to TV mode, 48fps, fully zoomed out
3. Frame something that is basically 50% zebra'd, 50% normal
4. Lock exposure - if you do this you'll end up with the full range of -11 to +11, at 1.8F
5. Change the exposure to +9.

At least with what I've been playing around with (which is well lit), this looks to me better then Cine-mode. I can't take any credit for these settings, they're all from Dennis at Cinevate (Brevis), and he fiddled around to find his favorite, and for my money I like them as well. It's also worth pointing out that for the 35mm adapter I have to zoom in a bit, which changes the stop to something like 2.6 (which is fine, since most of my lenses are 2.8's).

Anyway, not sure if anyone else will find this approach useful, but I figured it was worth pointing out at least.

Rumpelgeist

2007 July 31st, 20:11

From the video:

You have to be fully zoomed out to set aperture.
This is not true. You can set aperture at any zoom. The problem is that the largest possible aperture is known for sure only for full wide and for full telephoto. These are the numbers in the manual and on the lens. But you can find out maximum aperture for any given zoom position simply by experimenting. Obviously, if the aperture is smaller than f/3.0 then there is no gain, does not matter what zoom is.

http://www.elurauser.com/articles/manual_mode_aperture_table_hv20.gif

If it is larger than f/3.0 but smaller than f/1.8 then you have to do a "press photo button halfway" validation. Lock exposure, check current aperture, add "+1" exposure and check aperture again. If it got wider then there is no gain. If it did not change, then gain kicked in. Simple.

4. Lock exposure - if you do this you'll end up with the full range of -11 to +11, at 1.8F
5. Change the exposure to +9.
Did you mean to say "Change the exposure to -9"? Because otherwise what you are doing is meaningless. You already at the verge of gain to kick in at f/1.8, increasing exposure will increase gain. I assume that you want quite opposite, you want to make sure there is no gain.

zephyrnoid

2007 August 2nd, 14:59

I hate to do this.
Our generous tutorial poster is thanked for his effort. Unfortunately, it's hard to follow the movie and harder yet to refer to it in the field.
If someone is willing to help me, I'll put together a fast "Cheat Sheet" that anyone can follow quickly without the need for a video payback.
I can do the layout and screen shot illustrations if someone else can break the process down precisely in an ordered list.
Thanks!

Ian-T

2007 August 2nd, 15:36

http://www.elurauser.com/articles/manual_mode_aperture_table_hv20.gif

If it is larger than f/3.0 but smaller than f/1.8 then you have to do a "press photo button halfway" validation. Lock exposure, check current aperture, add "+1" exposure and check aperture again. If it got wider then there is no gain. If it did not change, then gain kicked in. Simple.

Thanks for the chart. Your explanation and this chart kind of makes things more clear for me now (I'm a more visual type of person). Before I did not know at what point, when in telephoto, gain kicked in.

lukaswit

2007 August 31st, 16:19

Could you tell me where I can enable a option showing an aperture and shutter on LCD like in this tutorial movie, because I can't find this option for few days.

drmadison

2007 August 31st, 16:56

Could you tell me where I can enable a option showing an aperture and shutter on LCD like in this tutorial movie, because I can't find this option for few days.

There's no option for that...
If you half-press the photo button (on the top of the camcorder) WITH a minisd card in the slot, it will show the aperture. I have until now had no minisd card in there so I just get the red "you have no card to take a photo on you idiot" icon flashing at me.

freeflight

2007 September 15th, 04:18

zephyrnoid

2007 September 15th, 08:39

hate to do this.
Our generous tutorial poster is thanked for his effort. Unfortunately, it's hard to follow the movie and harder yet to refer to it in the field.
If someone is willing to help me, I'll put together a fast "Cheat Sheet" that anyone can follow quickly without the need for a video payback.
I can do the layout and screen shot illustrations if someone else can break the process down precisely in an ordered list.
Thanks!

Rumpelgeist

2007 October 5th, 13:43

I read both Barry Green's article
http://www.dvxuser.com/V6/showthread.php?t=96502
and elurauser's article
http://www.elurauser.com/articles/manual_mode.jsp
To sum them up, both indicate that in TV mode of fixed shutter speed, HV20 will try to max out aperture first, then it will increase gain if max aperture still can't bring enough light. With this said, what's is the point of pointing to a bright light source, lock exposure, etc?
I have to confess: I am the author of the article on elurauser website. I found out this "press photo button halfway to read aperture" trick myself by playing with my Elura 100 camcorder, then I found Barry's article about the HV20.

I find Barry's article unnesessary complex and convoluted. I believe that there is no reason of pointing to light source. What for? Need to read current aperture? Press the photo button. Need to set aperture? Select Tv mode, choose shutter speed, then lock exposure and adjust to your liking, checking current aperture with photo button. Not enough EV range? Well, in this case you can point to a dark area or, conversely, to a bright light source just to set a different baseline for built-in light meter, then lock exposure. Then you can adjust exposure and the range will be different, but what is the point of shifting the range, say, to smaller apertures if you shoot in low light? You won't see anything.

In regards to locking exposure. The point of the exercise was to use the HV20 in manual mode and to control shutter speed, aperture and gain at the same time. Merely using Tv mode locks the shutter speed, but aperture varies automatically, and sometimes you do not want that.

But you don't have to lock exposure if you don't want to. You can force the camcorder to do it for you. Say if automatic aperture is f/7.3, you may want to bring it two stops down to f/3.7 for more shallow DOF effect. You cannot simply increase exposure because you will blow up your video, so you need to screw on an ND2 filter. Photo button trick shows where you are at.

Given a scene, the amount of light is fixed.
The exposure lock allows to lock the exposure (duh!) so when lightning conditions change slightly, like when you pan or when a person's black contour appears in a brightly lighted doorway the camera would not change exposure automatically. Also, if you shoot the same scene on different days, you likely want to stay at the same aperture to make video from different days look identical. Here exposure lock helps. You lock exposure on the first day and write down what settings you are using. On another day you set the camera into the same mode and add/remove lights if needed. Even if you shoot indoors, the lightning on sunny or cloudly day will be different.

Once you choose your desired exposure or effect (dark or normal or bright), there is really only one correct/good exposure (EV value).
Sometimes the camera may overexpose or underexpose in automatic mode, so you may want to lock exposure and take it one-two notches down or up. Also, you may want to go for an under/overexpose effect for artistic purposes. Granted, you can do the latter in post.

toxotis70

2007 October 7th, 06:09

If i have to do a shoot to a location with various lighting conditions, how do i lock the exposure ?

Noel

2007 October 10th, 09:51

This is great stuff. Anybody know if you can also do this for Sony's and Panasonics. Such as the panasonic sd1 or sony cx7. I found th Cine/24P/f1.8 + 1/40 no gain is very nice. Dark black noiseless background. Also anybody trie this with the Canon CL3 lighting?

scroll1

2007 October 30th, 21:33

thanks for the video tut.
Just a simple question though:
When you lock exposure on a light source, do you wait for the camera to adjust itself automatically to that light or do you point and lock before it gets a chance to auto-adjust? Is there a difference in the end result?
thanks

Nacho

2007 November 10th, 04:36

I found a GREAT tool to read the shutter speed, exposure, AND gain from the hv20:

http://translate.google.com/translate?u=http%3A%2F%2Fvideotreffpunkt.com%2Fthr ead.php%3Fthreadid%3D2488&langpair=de%7Cen&hl=en&ie=UTF8

It ROCKS!!!:hv20-smilie09:
Thanks to elCutty for that!

deerel

2007 November 11th, 14:01

Great guide. Love it!

seider

2007 November 14th, 18:35

so what i was wondering now was: if you do lock the exposure and appature after pointing it to a light, (and the apature is f.18) you cant see anything, and if you want to see something you have to increase exposure which increases gain. whould this happen in a better lit situation?

Ian-T

2007 November 14th, 21:49

Just increase the light and not the exposure.

seider

2007 November 15th, 12:28

Just increase the light and not the exposure.

by light you mean lighting of room. what if its outdoors? or would it already be bright enough if it was sunny outsize?

i wish i could test this my self, but i just got a new hv20, and i dont have the charger!!!:hv20-smilie36:

Jessica

2007 November 24th, 19:23

Thanks Patrick! veeeery nice trick! :hv20-smilie70:

funkg

2007 November 25th, 03:33

OMG i think canon just disabled the half press button trick on the newer batches! It's not working for me in film mode, even with a midi sd card inside arg! am i doing something wrong? The half button display does work when the camcorder is in camera mode, but not in video mode, which is completely useless to me!

tcindie

2007 November 25th, 04:01

it doesn't work while recording.. but it should work. I seriously doubt Canon has changed anything.

funkg

2007 November 25th, 04:50

man it's not working when stopped or paused. when I press the button half way I get this flashing red "off" symbol on the bottom left of the screen, what's going on here?

Worley

2007 November 25th, 05:17

Have you formatted the SD card?

funkg

2007 November 25th, 05:36

woosh, okay i figured it out. I had to go into func. menu and switch "STILL I. REC OFF" to "LW" mode... which allows you to take still shots while recording. Now I am able to get the half press to work!

David Zeno

2007 November 26th, 08:46

I am ashamed to say this, but I still don't get what the picture mode and manual control of the camera settings flows over to the video mode.... :hv20-smilie51:

I am guessing here, but are you saying you can go to picture taking mode, find a correct exposure, then take note of it, and then you switch to video mode
and then use this somehow in manual mode to get special effects ?

Sorry for posting maybe a dopey question, but I just don't get it :hv20-smilie50:

mazzimiliano

2007 November 27th, 08:19

I think it can be a good tutorial. Well, I'm not sure, 'cause I can't understand ANY word of what you said. :hv20-smilie50: I'm italian and you english is really only for english...

I watch many english tutorials and I understand almost all of them.

Anyway I'll try to listen to it many and many times to understand it, so thank you for the tutorial :hv20-smilie77:

(but for the next tut try to speak a better english please :hv20-smilie03:)

VideJo

2007 November 27th, 08:38

Try using a headphone while playing the tut. It helped me.

lasssman

2007 November 27th, 23:37

are you saying you can go to picture taking mode, find a correct exposure, then take note of it, and then you switch to video mode If you have the camera set to allow you to take stills while shooting video, you don't have to switch back an forth between video and camera mode - just push the button half down in video mode will give you the info.

nzo

2007 November 28th, 01:55

Thank you for your hard work Patrick...it's much appreciated!

John

mazzimiliano

2007 November 28th, 03:30

Try using a headphone while playing the tut. It helped me.

Yes it's true, thanks :hv20-smilie77:

So what you said is:
-go to TV mode and set to 1/50
-unlock exposure and point the cam to a light and lock the exposure
-point to the subject and set exp to -11
-increase exp till you see f1.8 and 1/50
-if you increase exp again there will be gain.

It's right?

:hv20-smilie77:

Jessica

2007 November 28th, 05:12

Yes it's true, thanks :hv20-smilie77:

So what you said is:
-go to TV mode and set to 1/50
-unlock exposure and point the cam to a light and lock the exposure
-point to the subject and set exp to -11
-increase exp till you see f1.8 and 1/50
-if you increase exp again there will be gain.

It's right?

:hv20-smilie77:
That is corect! :hv20-smilie77:

And if you have troubble finding a lightsource, you can use your cellphones LCD. :hv20-smilie64: You should use a white background / picture on your LCD when locking the exposure.

I don't know if your cellphone LCD is bright enough, but it works just fine with my sonyericson k750i.

africanmarty

2007 December 11th, 05:25

Hello all hope I get some feedback with this one,

Ok, this trick worked great for me ( without my 35mm adaptor ) no gain, just add more light and wala crystal clear footage without gain wich was great !

...until I wanted to get rid of gain when using my Letus 35 mm adaptor now when I put my adaptor on this is what I do :

Screw on letus adaptor
Zoom on to gg and focus sharply on gg
Place Nikon lens and focus the Nikon lens
Roll camera !!!

Now how do I do this without ANY possible gain ! As I have to zoom to focus on the gg and from what I read you must be zoomed out !! How are you fellow 35mm adaptor owners doing this trick with your adaptors to get no gain ?? I had a theory that I think works but would be happy to be proven wrong...

Setup 35 adaptor as explained earlier
Lock the exposure and aperture after pointing it to a light and keep at 0 (in other words once locked the level is left untouched at 0)
Add ALOT of light until the image produced by the camera is acceptable
Roll camera and try not to sweat too much from the heat :hv20-smilie29:

now would this be at f1.8 i cant tell since i had to zoom in to use my 35 mm adaptor ?? locking the exposure and aperture after pointing it to a light and keep at 0 will that lead to no gain but maybe less than f1.8 ???

hope you guys can help thanks alot

PS: is no gain the best for image quality if it can be appropratly lit ???

- Regards Marty.

zephyrnoid

2007 December 11th, 18:45

PS: is no gain the best for image quality if it can be appropratly lit ???]
Good golly YES!

mc74

2007 December 15th, 01:34

so when i pointed to a light and locked the exposure , my shot was much darker than i had expected. i had a 40w light and a 150w light in my room at night and when going through these steps, my footage looked pretty dark.

is my understanding correct that the hv20 is not that great at low light or indoor night scenes unless there is a ton of light or some (yuk) gain added?

xer

2007 December 15th, 19:29

Hi there!

This guide has really been useful for me in controlling the settings on the HV20. I have one correction I discovered for the author - he points out a "bug" in the camera that states that when you zoom in you CANNOT get the aperature down to 1.8 - he says it shows up as 2.2 when it is actually 1.8 - hence 'bug." I cannot totally confirm this, but I do not think there is any bug. I'm pretty sure this was set up intentionally by Canon due to limitations in the optics of the camera as follow:

If you set the aperature at 1.8 while zoomed all the way out, when you zoom in the aperature will close down - I thing when you zoom all the way in it will be at 2.4. BUT when you zoom out, it will return to the setting you started with, i.e. 1.8 when zoomed out completely. BUT if you set your aperature while soomed in (say, 2.2 if zoomed partly in), when you zoom all the way out you will STILL be at 2.2. The camera is giving you the setting you set it to, BUT is compensating for it's internal limitations. Thus, when the camera display says 2.2 it IS at 2.2. BUT if you set it while all the way out, you can get it down to 1.8. AS you zoom in it will stop the camera down and you'll noitce a visible change in the amount of light.

Using this data, I'm able to VERY exactly control my settings and get a really nice image.

xer

2007 December 15th, 19:32

BTW, another cool thing I got from visting this forum, is that, using this guide, PLUS using Cine Mode (24p), PLUS using a ND filter of .6 (two stops) along with a polarizer filter, I'm able to keep the shutter at 48 and get a really nice shot outside in VERY bright sun. The footage I just took at a local racetrack came out beautifully. I was using all Tiffen filters, including a Haze1, ND .6 and circular polarizer. Yes, I did get some vignetting when zoomed in a bit, but the over all effect was VERY good outside on concrete, with glaring sun.

This forum rocks IMHO, and I'm really glad it's here.

zephyrnoid

2007 December 18th, 22:49

OK Here's my final plea. Please could someone look at this cheat sheet and tell me if/how it needs to be amended. Thanks!
HV20 Exposure Hack
Plan D (Fixed Shutter & Gain Variable Aperture)
ACTION: EXP lock function
1) Zoom to Full Wide- With Fixed Illumination Cap
2) Cine Mode
3) HDV 24P
RESULT> Fixed Shutter Speed & Varied aperture range

EXP Shutter Iris Gain
+6 1/48 1.8 0dB
+5 1/48 2.0 0dB
+4 1/48 2.2 0dB
+3 1/48 2.4 0dB
+2 1/48 2.6 0dB
+1 1/48 2.8 0dB
0 1/48 2.8 0dB = Default Based On Target Illuminator
-1 1/48 3.4 0dB
-2 1/48 3.4 0dB
-3 1/48 4.0 0dB
-4 1/48 4.0 0dB
-5 1/48 4.8 0dB
-6 1/48 4.8 0dB
-7 1/48 5.6 0dB
-8 1/48 5.6 0dB
-9 1/48 5.6 0dB
-10 1/48 5.6 0dB
-11 1/48 5.6 0dB

zephyrnoid

2007 December 18th, 22:59

I will have to call Canon to find out what this is about. It could be that in cheating the HV20's 'programming' we may be throwing some things off.
Here's what my suspicion is:
- Zooms tend to let less light through the total optical system when set at Maximum tele (what you refer to as Zoom 'In'). This is NOT a function of aperture but of Luminance or the degree of light getting to the sensor. Keep in mind that aperture is the diameter of the iris.
- What I believe the HV20 does, based on your excellent observation, is it's programmed to 'report' that when set at 1.8 on full wide then zoomed in to full tele, the effective aperture is 2.4. This is a common programming function of all electronic 'feedbacks' of digital cameras.
I hate to be so nerdy about it but it matters because the Aperture is still 1.8, just that it's letting less light in, hence, effectively 2.4
- you go on to say "BUT if you set your aperature while soomed in (say, 2.2 if zoomed partly in), when you zoom all the way out you will STILL be at 2.2"
That's the real bug then! because if the system is properly programmed, it should go back to 1.8
Gotta call Canon.
Thanks for the report.:hv20-smilie77:

Hi there!

This guide has really been useful for me in controlling the settings on the HV20. I have one correction I discovered for the author - he points out a "bug" in the camera that states that when you zoom in you CANNOT get the aperature down to 1.8 - he says it shows up as 2.2 when it is actually 1.8 - hence 'bug." I cannot totally confirm this, but I do not think there is any bug. I'm pretty sure this was set up intentionally by Canon due to limitations in the optics of the camera as follow:

If you set the aperature at 1.8 while zoomed all the way out, when you zoom in the aperature will close down - I thing when you zoom all the way in it will be at 2.4. BUT when you zoom out, it will return to the setting you started with, i.e. 1.8 when zoomed out completely. BUT if you set your aperature while soomed in (say, 2.2 if zoomed partly in), when you zoom all the way out you will STILL be at 2.2. The camera is giving you the setting you set it to, BUT is compensating for it's internal limitations. Thus, when the camera display says 2.2 it IS at 2.2. BUT if you set it while all the way out, you can get it down to 1.8. AS you zoom in it will stop the camera down and you'll noitce a visible change in the amount of light.

Using this data, I'm able to VERY exactly control my settings and get a really nice image.

xer

2007 December 19th, 23:10

Hi there!

Let me clarify something - I never stated that when setting the aperature to 2.2 while zoomed in, there would be no reason for the camera to automatically open it to 1.8 when zomming out. The camera is remembering the LOWEST setting you entered, which if zoomed in, might be 2.2 or 2.4, whatever. When you zoom out, the camera will simply remember that setting. BUT if you are zoomed out and set the aperature at 1.8, THEN zoom in, you will see it close to 2.2, 2.4, whatever. THEN when you zoom out it will return to 1.8, because the camera remembers that this is the setting you chose. There is no "bug" in the camera. The camera is just remembering what setting you started with.

nickdmp

2007 December 29th, 08:42

So, if I do all this, and I have, and when I point at my subject and begin increasing exposure whilst checking using the half press, if I get to 1.8, then STOP. Don't add any more. If you do, you add gain.

If at that point my image is too dark then I need more light in the scene.

If I can't get it to f1.8 on max exposure then again, I need more light in the scene.

So far, much better images than before in low light.

I hope this is right?

Also my footage (captured on a mac using DVHSCap) is quite jerky when played back using this method. Anything that can reduce that?

Great forum, learning lots and getting better footage for it too!

rozroz

2007 December 30th, 12:24

bishaway

2008 January 1st, 19:52

I was wondering if there is a way to save the exposure settings so when the camera is turned off I don't have to set it up all again? Couldn't find anything when I did a search on the forum.

Cheers,

Ian-T

2008 January 1st, 20:13

I was wondering if there is a way to save the exposure settings so when the camera is turned off I don't have to set it up all again? Couldn't find anything when I did a search on the forum.

Cheers,

Unfortunately there is no way to save it.

Ian-T

2008 January 1st, 20:15

i'm trying the exposure lock trick right now..
first off all-
if it's 25p cine mode PAL- then i'm aiming at 1/50 -
NOT 1/48... right?
the other thing i need to know-
i'm fully zoomed out, then-
i aim the phone to cover the lens-
then i lock the exposure...

am i missing something?

tnx
Yeah...you are PAL so it will be 1/50 shutter.

And yeah that's how you lock it....make sure you have a mini SD card in your cam so you can see the aperature setting you are at.

jpc

2008 January 13th, 18:42

I only get the sound but no movie. Anything I can fix on my end?

David Zeno

2008 January 19th, 22:20

Very neat technique, now I gotta pull out the HV20 and try it out.

thanks for posting !

nolonemo

2008 January 30th, 19:07

Just want to make sure I understand this trick correctly....

I take it that in Tv mode at any given shutter speed, the HV20 will try to achieve correct esposure by opening the aperture, and, if there is still underexposure with the aperture wide open, then and only then will add gain to get to the right exposure. Correct?

So, at any given unlocked exposure setting, if the camera has set the aperture (assuming zoomed to full wide) to anything smaller than f1.8, the camera is not applying any gain. Correct?

Thus, the (only) real usefulness of the trick is to establish a zero-gain baseline that tells you whether you have to add light in order to get correct exposure without the camera adding gain. Correct?

Thanks, all.

Charles Lowthian

2008 February 1st, 04:13

I want confirmation on your other points too as that is my understanding.

As for:

Thus, the (only) real usefulness of the trick is to establish a zero-gain baseline that tells you whether you have to add light in order to get correct exposure without the camera adding gain. Correct?

Correct. The usefulness of this 'trick' is to be able to control gain (at the max aperture). Which is highly useful in situations where you can control/modify lighting, and choose the grain level / 'purity' of your image.

I don't think there is a way to add/decrease gain at any other apertures (eg: f5), is there?

TradeMark

2008 February 1st, 14:56

All this info has been awesome. I guess theres still some concerns that I have.

If there is any gain to begin with its because of low light, correct? So if you find the 1.8f where gain is 0 the chances are that the shot is going to be dark since no gain was applied. At that point, aren't you going to have to now add lighting to your scene? If thats the case, why bother with this if you already know that low light was the issue to begin with. Is this only to determine if gain is being applied at all even in a possibly low light area? Is the ultimate goal to be able to shoot with zero gain with as little light inorder to achieve a "night" or "dark" scene? Sorry if im not being clear but I guess this is a little confusing as to the ultimate purpose. But I love the idea of finding the zero gain. Either was its an awesome technique to get the info.

Ian-T

2008 February 1st, 15:09

You are right...and that's a good question. Yes...this should tell you to add more light to your scene...but I find soometimes even in good lighting situations you can still get noise in some of the dark..or shadow areas. This method will help you to try and get an overall "cleaner" looking image.

But to be honest... not all gain is bad.

bmoore

2008 February 1st, 17:14

Guys:

When performing this procedure and using a wide/tele lens, do you do this before or after you add a lens/filter?

Thanks

Brian

UPDATE: NM, Erik already gave me all the info I needed. Thanks Erik!

Lederhosen19

2008 February 2nd, 13:04

Ok, so I watched the video on how to control the shutter/aperture/gain, but I don't get it. In the video, when he changed the aperture after locking the exposure, it was really dark. So whats the point? In outdoor areas thats probably fine, but in indoor/low light areas that doesn't work. But people have said they used that in low light and it helped.
Can anyone clear this up? I'm really confused...:hv20-smilie51:

skiltrip

2008 February 5th, 08:30

I have read a lot on here regarding the "light trick" to lock exposure and control aperture, and watched the video tutorial on it.

I've managed to be able to reproduce this pretty well, but I have a few issues I'm unclear about as to what's actually happening.

Question 1: So, when I'm in Tv mode, shooting 24p, set my shutter to 1/48, point at a light and successfully lock myself at 1.8, giving me the full -11 to +11 range for exposure adjustment, do I get a little gain for each +1 I add? In the tutorial he explains it that way, but I've also read when you lock your exposure, you lock out any gain from happening, so I'm unclear on this. It seems to me is HAS to be adding gain, or else where is it getting that extra light from?

Question 2: Where is an ideal aperture to lock at? Is it ideal to lock at 1.8 and have the full -11 to +11 to work with, or is it better to lock at a slightly smaller aperture, say 2.2 or something? I know this may depend on what i'm "going for", but give me one example of it and I'll be able to apply that to whatever situation(s) I'm working with.

Question 3: I'm pretty sure this has been clarified, but I just want to double check. I CAN use this light trick in Cinemode, correct? You just have to make sure when you lock your exposure you not only get your correct aperture, but you need to make sure it locked at 1/48 too, right? I think I've managed to do this, but I'm not convinced that that 1/48 shutter speed is truly locked. Would changes in room light affect the shutter speed, or only zooming?

thanks everyone taking the time to read this and clear up a few things.

- kip

Kanttori

2008 February 7th, 10:39

I'd love to get an answer to skiltrip's qustions, too!

madphill

2008 February 7th, 22:43

It was my understanding that you were almost forcing a wider aperture that the camera wouldn't normally make available in that shutter speed.

If you slow the shutter speed due to low light than you get grainy, blurry footage...so adding the couple of stops on the aperture improves the image.

Am I totally off Patrick? I'm not 100% sure either, but after a few tries I got your trick to work, sans the aperture/sspeed checking. Apparently if you don't have a MiniSD in, it won't do that???

Alex_MD

2008 February 8th, 03:58

nolonemo

2008 February 8th, 11:58

I don't get the purpose of this trick: in low light camera opens aperture wide open (f1.8) automatically, so there is nothing you can do about light. Does this trick allow to reduce/increase gain in wider range to make footage darker-and-clearer/brighter-and-noisier?
thanks.

The basic theory is that you lock the camera at a setting where it's not applying gain, and then adjust the lighting so that the exposure is correct (i.e., if you were shooting indoors, you would add more lights on the scene)

Ian-T

2008 February 8th, 14:58

In addition to what nolonemo said the reason is also to try and lock your footage in 1/48 shutter for cinematic purposes when using Cinemode. Cinemode's shutter is unpredictable...and if your purpose is to use a 180 degree shutter, for that film look, then locking it this way will help. the main purpose is however not to add gain....or control the gain to a certain degree...like I said before....gain is not necessarily evil...uncontrollable gain is.

rozroz

2008 February 9th, 05:05

and what if i want to add a little gain while locking exp. on cinemode (assuming i decide to only use cinemode)?
i mean, i can get up to 1.8, 1/25 shutter (it doesn't stay locked on 1/50 so i have to use 1/25, right?)-
so there's no way to add, let's say, 3db of gain? (which mean two more pushes after the 1.8 1/25 limit)

can this be done on CINE at all? or only on TV?

GeeksGoneBad

2008 February 13th, 08:01

Here's my experience so far on this - I think I'm close :)

I am in Cine mode and 24P - I put a white picture on my cell phone and completely cover the lens and then lock the exposure... Here's my chart

+11 f2.0 1/48
+10 f2.2 1/48
+9 f2.4 1/48
+8 f2.6 1/48
+7 f2.8 1/48
+6 f3.2 1/48
+5 f3.4 1/48
+4 f3.7 1/48
+3 f4.0 1/48
+2 f4.4 1/48
+1 f4.8 1/48
0 f5.2 1/48
-1 f5.6 1/48
-2 f5.6 1/48
-3 f5.6 1/48
-4 f5.6 1/48
-5 f5.6 1/48
-6 f5.6 1/48
-7 f5.6 1/48
-8 f5.6 1/48
-9 f5.6 1/48
-10 f5.6 1/48
-11 f5.6 1/48

So I guess I need a slightly brighter cell phone? I'd really like to get that up one notch or two to be "just right" wouldn't I?

Jamie

rozroz

2008 February 13th, 15:59

it doesn't matter... getting to 1.8 is a very minor change..
if you lock it on 2.0 or in the area,
then going higher would cause a 1/24 shutter (which suppose to be bad), so either way you stay limited to the 2.0 or 1.8 max aperture.. that's almost what you've done anyhow

Dennis Vogel

2008 February 17th, 15:51

Can anybody with a better English or ear than mine, tell me please what is Patrick saying at 02:28? It's the most important thing: what to do with the camera for having access to the manual control of the gain.
I guess one have to cover the objective, so no light goes inside, but I just can not understand what he is saying.

Starting at around 2:17 here's what I get:

... you're still adding gain and we can't control the aperture. To get around that you unlock the exposure and point the camera at a light then you lock the exposure again.

Does that sound about right?

Good luck.

Dennis

bimpatiens

2008 February 18th, 09:30

BTW, there is a way to disable the AGC. Hint: the camera is then limited to daylight white balance.
Sorry - I've read the thread, but I seemed to have missed any follow-up to this "hint"? Just to ask the 'dumb' question, what is being suggested here?:hv20-smilie49:

ChrisK

2008 February 20th, 08:32

Hi everybody.

I just bought a HV20 and I really expect to do great movies with it. I already ordered the Twoneil 35mm adapter wich looks great.
I was wondering how to control the grain on my cam and I found this post. Unfortunatly, each time I try to read the Quicktime video, my computer crashes and I have to reboot.
Is there any possibility that someone upload it on a video sharing website like Youtube, Dailymotion or Vimeo so I can see it online?

Thanks in advance.

warden

2008 February 20th, 08:41

try this link - not the film but it details the method
Click Me (http://hv20.com/showthread.php?t=4195)

ChrisK

2008 February 20th, 11:37

thanks. By the way, I saw this link with the text explaination but as I'm french and all this vocabulary is a bit technical, it could be helpfull to see it "in action".

Hillebrand

2008 February 23rd, 13:06

Hello Patrick
I douwn loaded your video but can only get sound, is something missing on mij machine

Hillebrand

2008 February 23rd, 13:15

this is a tutorial i made a few days ago on how to control the aperture and gain on the HV20. i had been up for about 20 hours so you can tell I'm a little muddled and tired. so if someone else want to make a better one that's more clear, please do so :)

this is the PAL version, so it's basically exactly the same but the NTSC version would have different shutter speeds.

you need a miniSD card in your camera for this to work.

http://hv20.info/yopu/hv20aperturecontrol.mov

mirror - http://www.megaupload.com/?d=JNDHJMN5

i prefer to use cine mode because you get the extra shutter speeds if you need them. you get 25, 29, 33 ,40 and 50 where as you only get 25 and 50 in TV mode.
video tutorial on how to control the shutter/aperture/gain

I dit download ok but can only get sound. What is missing on my machine

bimpatiens

2008 February 24th, 18:19

can only get sound. What is missing on my machine

Sometimes if I hit PLAY again, and then CLICK on the black part of Windows Media Player, it works. It's probably a feature.

Eugenia Loli-Queru

2008 February 25th, 04:29

DiscoStu

2008 February 27th, 08:36

quick question: are u all seeing the aperture and shutter speed settings while u record?

or only while paused?

GeeksGoneBad

2008 February 27th, 17:08

only when paused and pressing halfway down on the photo button

Alsone

2008 March 6th, 19:37

I don't know if anyone has posted this before, but I came across this on vimeo.

This guy has shot footage in his car at night with and without the exposure gain locking trick.

Whilst the video is a little boring to watch (far too long in the 1st half) the results are interesting and a good illustration of how zero gain really cuts back the artefacts:

http://www.vimeo.com/404844

Eugenia Loli-Queru

2008 March 10th, 18:43

That video is nothing but UNDER exposing. Sorry, I had to blog about this, it kind of bugging me people falling for it without understanding how cameras work: http://eugenia.gnomefiles.org/2008/03/10/the-god-damned-hv20-cellphone-trick/

Lunchbox

2008 March 10th, 19:16

I ain't no expert on this topic but I did try. While I still have lots of questions in my mind using this trick, I can see it gives really clean grain-free video. Isn't that great already? Whether it is underexposed or not, it could be subjective and also a shooting style.

I read your blog. The part about zooming in to a white point and perform a manual white balance. That's just white balancing. It won't lock the exposure. Once you zoom out, the auto exposure kicks in controling the aperture, shutter, and gain. (Or do you mean to lock exposure right after zooming out?)

Eugenia Loli-Queru

2008 March 10th, 19:33

Yes, you need to lock exposure after zooming in, and compensate based on the brightness of what you zoomed on. You must be on "P" mode, of course.

Lunchbox

2008 March 10th, 19:46

No it doesn't work. I am in a poor lit room (yes, the bathroom). When all the way zoom in to a bright white object (towel), the video is all grainy. So I have to give a light source... let's see what comes handy.. oh my cell phone.

I don't see your method work (at least I tried and it doesn't give me the clear video I can get). When locking the exposure during all the way zoomed in, the aperture is at F2.8. From what I understand, each F-stop value increase will add 1.5db of noise gain. So locking at F2.8 will not be noise free. F1.8 will be.

Eugenia Loli-Queru

2008 March 10th, 19:57

Taky, try again. This time do NOT use a cellphone. Just use another bright object that BELONGS to the scene. And then, after you set the exposure/wb, then under-expose lightly using exposure compensation.

Locking the exposure doesn't change the number of photons that hit each pixel, and that's the primary source of noise.

But what you're saying has nothing to do with exposure lock - you say that you prefer to shoot at a larger aperture (and with a comparably lower gain). That indeed reduces noise, but it's not an apples-to-apples comparison since it changes the DoF and blur.

Lunchbox

2008 March 10th, 20:56

Just tried. Didn't work well AT ALL. I zoom in all the way to the night light. Manual white balance in P mode. Lock exposure. Zoom out. The video is really dark. use the joystick move all the right to the right change exposure. Even at the brightest setting, the video is really dark. Besides, setting the white balance at a night light changes the entire tone of the video after I zoom out.

So I do the cell phone trick. viola! the video is a littie bit brighter with no grain visible. I can still move the joystick to the right a few step to add brightness.

I also tried out the way Lou pointed out using Spotlight mode

http://www.hv20.com/showthread.php?t=7492

Similarly, the outcome is really dark. I like what Ian suggested using Night mode. I got really good result wiht it too.

http://www.hv20.com/showthread.php?p=62702#post62702

Maybe your method works well for you and some other. After all, it's just some tricks we play around with. There could be no right or wrong here. Whatever ways work with you, go for it.

Thank you for explaining the steps so I can experiment. I would still prefer the cellphone trick at least I don't have to dig around the menu to get to WB command.

Eugenia Loli-Queru

2008 March 10th, 21:11

Look at the scene at 1:27 here http://vimeo.com/451992 , my second suggested method was specifically used. It worked fine.

Besides, I don't understand why you used a night light to set the WB. It must be a white/gray point. E.g. if you are experimenting in your bathroom, use a white or gray towel, not the night light. This method is simply trying to emulate a gray card, when you don't have one, or when you try to shoot too far away from the camera. If the whole room is so dark that you can't see anything regardless, you should not be recording there in the first place.

Lunchbox

2008 March 10th, 21:19

I told you I try white towel. When I zoom in all the way, it is already very grainy. WB on the grainy scene and lock exposure gives really bad result. It is not a complete dark room. There are natural light coming in and the night light. It's just a very well lit situation.

I think the cellphone tricks works well as it tricks the camrea thinking there is enough light so gain will not kick in. That's just simple and stright forward. However, I don't know performing manual white balance will lock the gain at 0db. But there're proves that locking aperture at F1.8 with sufficient light will generate no gain.

I looked at your video. It's very nice. The scene particularly on 1:27 I don't see any special about it. it's underexpose because there aren't enough light. I think as long as we can get grainless noise-free video, that matters.

Eugenia Loli-Queru

2008 March 10th, 21:28

Well, that only makes sense if the exposure compensation doesn't follow the same program curve as the exposure. Now, if indeed the exposure compensation follows a different program, *and* if that program doesn't change the gain, *and* if the regular program changes the gain before going wide-open, it makes some sense, but none of those assumptions are documented anywhere.

Lunchbox

2008 March 10th, 21:35

when you said "exposure compensation" do you mean you move the joystick left/right to adjust the "locked exposure"? I personally believe that will induce noise. If the aperture and shutter locked at the same value, and the scene gets brighter, it's done by "gain" obviously.

Is there anywhere it's documented performaning manual white balance will lock the gain level at 0db? I'd like to know and learn more.

Using the cell phone trick already gives pretty good result without even need to move the locked exposure up and down. After all reading your blog and experiment it by myself, I wouldn't call this cellphone trick "stupid". At least it's quite practical :)

Rumpelgeist

2008 March 10th, 21:54

I ain't no expert on this topic but I did try. While I still have lots of questions in my mind using this trick, I can see it gives really clean grain-free video. Isn't that great already?
Taky, here is a post I did last year: http://www.hv20.com/showpost.php?p=12588&postcount=52 It refers to an article I wrote on the subject. Or, here is the direct link to the article, I posted it three pages earlier, that was like 8 months earlier, and people seem to be lazy to read the whole thread: http://www.elurauser.com/articles/manual_mode.jsp Here is the same graph, for your and other's convenience:

http://www.elurauser.com/articles/manual_mode_aperture_table_hv20.gif

The point is, cell phone or, umm, a $20 precision lightning tool containing just a small battery and a light bulb, are intended to set the camera into a certain aperture/gain range, but if you shoot in a dark room and cannot up the lights, what is the point to shoot a barely legible picture? Just to brag that it was shot with no gain? I explained in the article how to get rid of gain, just wiggle Exposure one step down/up and see if aperture has changed. If not, then gain is activated, as simple as that. Then to get out of "gain zone" you need to decrease Exposure, checking aperture value all the way. When you see that aperture value increased, then you are definitely in a gain-free zone.

http://www.elurauser.com/articles/manual_mode_f11-60.jpg

Here is a simple rule: GAIN IS NOT ELEVATED UNTIL IRIS IS FULLY OPEN. Here is how Panasonic cameras use this approach, I think the GL2 works the same way: you are opening iris, aperture goes like 3.0, 2.8, 2.6, 2.4, 2.2, 2.0, then it displays "open" meaning that aperture is maxed out and the iris is fully open, then if you persist with increasing exposure, the camera starts elevating gain. The readout now displays "open" and gain value in dB. Canon cameras work in exactly the same fashion! Only these consumer cameras do not emphasize the aperture-gain relationship, and do not display numbers unless you half-press Photo button. You won't see gain, but you will see aperture, so you need to "dance around" to see whether it changes or not when you are changing exposure.

I am amazed that people still discuss the useless cellphone "trick" which sets the camera into one specific EV range, which may not even be optimal. Also, it does not guarantee that the camera is set up to max aperture yet to zero gain. You still need to check current aperture with Photo button, which mitigates the whole effect of cellphone trick.

At the same time, Eugenia's method does not guarantee the specific f-stop/gain either, which is why it is pretty much useless too. Use the freaking Photo button, and the happiness be with you.

The actual "trick" is not that a cellphone sets the camera in an optimal mode. The real trick or may I say, a blessing, is that the Photo button provides the readout of the built-in light meter, the readout for current shooting conditions, right here, right now, without the need of shooting a test picture or video, and then analyzing its metadata. This is almost a semi-pro feature -- comparing to dumbed down camcorders of present days -- of many Canon cameras, including my cheap Elura 100 and my recently purchased HV30.

Lunchbox

2008 March 10th, 22:10

I actually don't use my cellphone. I use a keychain LED light. What I did is to bright up the entire frame. Check the photo button. Then I move the light away from the lens and keep checking the photo button. F value started to drop. Once it goes down to F1.8, I locked the exposure.

I can see that's the way to ensure there's no gain because the LED light is bright enough to cause the camera to resize the aperture size because of too much light. In that case, gain will for sure won't kicked in.

What I don't agree with you is that

"what is the point to shoot a barely legible picture? Just to brag that it was shot with no gain?"

There are scenes in movies, music TV or TV shows. Just for an example, an actor laying down in bed in the bedroom with complete light out. There's only limited light coming out from the window. That's a barely lighted scene and grain-free. Look at this video too

http://www.vimeo.com/456706

Eugenia Loli-Queru

2008 March 10th, 22:23

>Just for an example, an actor laying down in bed in the bedroom with complete light out.

They are shot WITH lights. With enough lights to not cause gain, and their cameras have big sensors that perform better in low light than the HV20 anyway.

Another example is the Matrix dark scenes. If you see behind-the-scenes scenes of these shots you will see that they were properly lit all the way through and all the dark-iness is added in post.

As for this guy's vimeo post, he used 1/48th shutter speed, which helps with noise. Low fps and low shutters will help with gain. Besides, he might still have noise, we don't see an HD full scale version of that video on Vimeo, neither he offers the original file for download.

phanatik

2008 March 10th, 22:26

I haven't got it yet either. im still getting alot of noise(gain). So much so I can almost hear it.

Please help.

Eugenia Loli-Queru

2008 March 10th, 22:42

>Please help.

I can send you $30 towards buying lights and a better camera.

Lunchbox

2008 March 10th, 22:43

a $30 camera???!?!? hehe

Rumpelgeist

2008 March 10th, 23:13

I actually don't use my cellphone. I use a keychain LED light. What I did is to bright up the entire frame. Check the photo button. Then I move the light away from the lens and keep checking the photo button. F value started to drop. Once it goes down to F1.8, I locked the exposure.
Exactly. OR, you can lock exposure right away, does not matter that aperture is too high (in your case). Seems that people forget about EV scale, the whole whopping 11 steps to the left and 11 steps to the right, almost 6 f-stops across the board. You can simply begin decreasing exposure until you hit F1.8 (assuming that the camera is full wide). That is it, no need to move the light closer/farther from the camera. Of course, if your light is too strong, this won't work, but this gives an idea.

Eugenia Loli-Queru

2008 March 10th, 23:20

>a $30 camera???!?!? hehe

I said "towards", not "to". It implies that he will have to pay up the rest. You need a big sensor camera to have better light performance, e.g. the RED. Therefore, it's cheaper to buy lights.

Aaron Courtney

2008 March 11th, 15:08

I feel a couple of relevant points have been lost here in this discussion. First, it's easier to appreciate this whole procedure from a full manual SLR mindset. Back in the day when we all were pushing Kodak's brand new T-Max film to see how much we could get away with, you learned the value of duplicability and using a method that yielded consistent results. Shooting full manual using a lightmeter and the Zone system got you there every time under any lighting condition.

That's the whole idea behind using the same light source when locking exposure - being able to replicate the exposure scale in any envronment. Doing so effectively gives you a full manual camera, not unlike having an actual aperture ring on the lens and a shutter speed dial. If you use various lighting sources from scene to scene to lock exposure, then your scale "ticks" will be inconsistent. That would be like having f2.8 in one click on the lens under one lighting environment become f5.6 in a second lighting environment with everything else held constant. That's not how you would want to operate a fully manual camera (you'd go nuts trying to reconcile between your light meter and your camera because the calibrated settings are now "un"calibrated), and if you're going through the trouble of ensuring gain-free exposure with these consumer video cameras, that's not how you're going to want to use these things either.

Additionally, depending on the intensity of the light source, you won't get the full -11 to +11 scale. That just decreases your options and isn't good in any way. That'd be like stripping the ability of your SLR lens from stopping down to f8, 11 or 16 - not exactly what you want to have happen when your ability to focus precisely is impaired and additional DOF will give you the latitude you need.

So, coming from the standpoint that you're trying to avoid gain yet maximize your flexibility WRT aperture settings while maintaining your desired shutter speed, it's clear that (1) you need to be able to duplicate your exposure scale clicks under all shooting conditions and (2) you need to have the widest gainfree +11/-11 scale at your disposal. By being able to perfectly replicate your exposure scale, you could print out a small card documenting what each "click" on the exposure scale yields and then use your lightmeter to click in perfect exposure every time. I'm guessing centering the whole exposure scale around f4 or 4.8 would yield the most useable gainfree/constant shutter speed clicks on the exposure scale. Very brightly lit outdoor scenes would most likely have to be tackled using an appropriate external ND filter since you would most likely be preventing the cam from utilizing its own.

Rumpelgeist

2008 March 11th, 15:41

Aaron, I think we should divide the goals that one might want to achieve:

* getting rid of gain
* having full EV scale from -11 to +11
* having constant and reproduceable EV scale

As for getting rid of gain, one should use Photo button for true real-life settings/measurements. In Tv mode with auto exposure, the Photo button will display automatic metering. With locked exposure, the Photo button will display current settings you are shooting with, including aperture and shutter speed. You can find out whether gain is kicked in by "dancing around" your current EV setting. If your lens is not at full wide, you'd rather have aperture value at F3.0 or larger to guarantee that gain is not elevated. If you use the external light source to set up the scale, it has to be very precise. I would not trust a cell phone or a light bulb from Erector set to produce constant and precise light for this purpose, I would verify with Photo button anyway, which makes cell phone trick meaningless for me, but maybe it makes sense for others.

For having full EV scale, I am not sure that this ALWAYS makes sense in dimly lit conditions. You put light to the lens, lock exposure, then... you cannot see a thing because either iris is not fully open or gain is at zero, so barely anything is being recorded. You will have to increase exposure anyway to get something on tape. But more likely you would want to reduce exposure to get rid of gain, then why would you want the whole +11 steps for? But I hear you, you might want to have a full scale for whatever reason, no problem. I still think that you don't need a special light for that, but if you have one, good for you.

For having the consistent EV scale, I agree with you. This has little to do with gain, but more with internal ND filters. From my experiments with the HV20 (I will experiment more soon, when I receive my new HV30) it tries to stay around F5.6. Apparently, at this aperture the picture has the best quality with lowest optical distortion. The camera uses internal ND filters to compensate for brighter conditions. If you lock EV scale somewhere around F5.6 and then change EV lower/higher, you will notice that it stays at F5.6 for 5 or 6 EV steps, this is about 1.5 f-stops. so if you are shooting at conditions when your aperture is around F5.6, you may want to have consistent EV scale from shot to shot to ensure the same combination of aperture and ND filter. This goal is different from getting rid of gain, and requires a different light source, more powerful one. Again, would you trust this source for producing consistent amount of light? As I am not shooting feature videos with multiple takes, I don't care THAT much for consistency :) If I did, I could just wiggle 5-6 EV steps each way and see how "ND filter zone" is located in relation to EV scale, from there I could make needed correction. I see how this can be a pain.

exte

2008 March 11th, 16:20

If I could shoot 24p at 1/48 shutter with no gain I would be a happy guy. It wouldn't be about 'underexposure' for me since I would ensure I'd have adequate lighting. Some of us just don't like gain, that's all...

Aaron Courtney

2008 March 11th, 17:04

Agree completely Aramis. For me, personally, all three are preferred and that's how anyone coming from a full manual film background would approach this subject. As a kid, these principles were drilled into me since my dad was shooting professionally. You kinda learn through osmosis if nothing else. Of course having a full color and B&W darkroom in your basement certainly doesn't hurt because you get to see the results of every step in the process firsthand. Additionally, unlike video, there is no realtime feedback, so you've got one chance to get it right. And that's why you carried a couple of really good light meters and a gray card (along with the zone settings) with you everywhere you went because there is no "do over" with film.

With video, it's too easy to get lazy because the urgency doesn't have to be there with decent auto exposure. But there will be times when the cam is fooled and that's when you're going to have to fall back on your fundamentals. My point is, if you're comfortable in those situations, you may as well shoot that way 100% of the time.

The whole stopping down via ND filters vs. closing the iris is unfortunate. But at least the shutter speed isn't increasing! (Thankfully, Canon's AF is very good - have had trouble with following kids sledding down a ski hill in bright daylight, though. Forget manual focus there anyway, you have no chance, LOL).

Rumpelgeist

2008 March 12th, 20:57

Hi. I'm new to this forum, but I notice a problem with the exposure lock trick that I'd like to bring to your attention. I've installed an SD card so that I can track the settings, and I followed the instructions presented in other posts. However, I have noticed that even if you lock the exposure, settings will change when you move the camera or zoom in to frame up a shot. If you're in Cinema mode, the shutter speed will change, and if you're in TV mode the exposure will still slide around, even after "locking" with the joystick. Has anyone else encountered this?
The zoom lens on most er... cheap camcorders like the HV20 has variable speed. It is f/1.8 at full wide and f/3.0 at full zoom. So if you locked exposure at wide setting and then zoom in, the camera will decrease aperture. To maintain the same exposure it may slow down shutter speed. Remember that in Cinema mode none of parameters is locked, only the whole combination of aperture+shutter_speed+gain+ND_filter is locked, so the camera can compensate change of one parameter with another.

The easy solution is to use Tv mode and aperture narrower than f/3.0 for all your zoom-in & zoom-out shots.

Lunchbox

2008 March 12th, 21:21

I think the zoom range changes the aperture value from F1.8 to F2.8

Rumpelgeist

2008 March 12th, 21:37

I think the zoom range changes the aperture value from F1.8 to F2.8
The manual specifies F1.8-F.3.0, but you may be correct. I don't have my HV30 yet, but my Elura 100 goes from F1.6 to F2.4 while the manual specifies F1.6-F2.6 I am ok with this sort of errors.

kruzer

2008 March 12th, 22:03

Not only hard to understand the manual... it is set the smallest type and on tissue paper that makes it even harder to read.
Canon should also hire some people who can proof read their manual and express it in a better term.

However, at least the hardware is nice:)

DiscoStu

2008 March 13th, 07:53

i like the trick.

forces me to control the scene (lighting), not the scene controlling the camera.

use it all the time.

ashbank

2008 March 14th, 13:12

Question: What do the 'seniors' here feel about using Barry Green's method of simply keeping the lens cap on, full wide, and then locking exposure? Simpler than relying on a cellphone lcd or bright white source at site, isn't it?

koolpenguin89

2008 March 14th, 13:20

Well, ignoring the fact that the HV20s lens cap is automatic, and thus cant be activated in camera mode, id like to point out that a lens cap would make the cam kick the gain all the way up, which is what we are trying to avoid.

Dylan

ashbank

2008 March 14th, 13:45

I meant an external lens cap. I use the one that came with my Canon Wide Converter lens, while keeping the wide lens on the hv20, and I get very decent results, virtually no gain, not too under exposed even in low light, and nice colour density. I got the lens cap idea from this tutorial here:

http://dvxuser.com/jason/hv20/

Arla

2008 March 14th, 17:24

Pointing at a light seems to be a bit of a red herring in some situations. Taking video in my living room (which isn't bright, but isn't too dim) if I point my camera at a light I end up screwing it so far to one end of the spectrum that I can't get to 1.8 because the light was brighter than the rest of the scene.

Overall it seems like the easiest method is just set the shutter (1/48 on mine, 1/50 on PAL I think it is), then point at a brighter thing in the scene (the white fireplace in my case) and then click manual exposure, use left and right (increase/decrease exposure) to find the point where you hit 1.8f, any higher exposure and you are adding gain, lower and you will reduce apeture (think I got my terms right there, sorry still learning a lot).

If you click on manual exposure and then reduce exposure to -11 and it's still reading 1.8 you know that you are probably adding gain no matter what (or will have a VERY dark scene). If increasing gain to +11 you still have an f stop number greater than 1.8 you know the scene is light and you won't add gain.

At least that's my 2 cents from my playing.

Aaron Courtney

2008 March 14th, 17:24

LOL! ashbank, if you like the idea of repeatability of exp settings, then you've got the right idea. Check out lytecap.com for info on a product that is being developed right now that will probably meet with your approval.

You can follow the development thread at dvinfo.net in the HV20 forum if you'd like...

ashbank

2008 March 17th, 03:14

Thanks, Aaron. The lytecap sounds interesting. Will follow the development thread, thanks for the tip.

CycleWriter

2008 March 19th, 01:40

I finally got in a nice comforatable position last night and dug into the HV20 book. I find the explanations & illustrations on how to do things with this camcorder very hard to follow & I'm a technical person. Is it just me, or are others finding the book to be hard to follow. In my other life as a magazine writer/photog, I am a technical editor and I find the Canon manual to be very vague and lacking. But that isn't something unique to Canon, from my experience. :hv20-smilie49:

I don't just want to know how to move/change something. I want to know what it affects, specifically, and in what situations I will want/need to move/change something. I guess that's for the book writers to do. Thankfully we have this forum dedicated only to the HV10/20/30. I wish Magic Lantern would do camcorder guides like they do still camera guides. :hv20-smilie119:

milespapineau

2008 March 27th, 17:11

i tried this for 2 hours and heres what i got
-11 (EXPOSURE) = f4.8 ( 1/60 NTSC )
-10 = f4.4
-9 = f4.0
-8 = f3.7
-7= f3.4
-6 = f3.2
-5 = f2.8
-4 = f2.6
-3 = f2.4
-2 = f2.2
-1 = f2.0

+0 = f1.8

+1 = f1.8
+2 = f1.8
+3 = f1.8
+4 = f1.8
+5 = f1.8
+6 = f1.8
...And so on until +11 (BTW +11 = f1.8 )

milespapineau

2008 March 27th, 17:15

omg im so stupid, i thought he said f4.4

Rumpelgeist

2008 March 27th, 17:22

i tried this for 2 hours and heres what i got
This is 4 minutes 27 seconds per EV step. Bravo!

milespapineau

2008 March 27th, 17:28

congratualtions u can use a calculator, i meant that u read about different techniques of doing this and tried different ones for 2 hours

milespapineau

2008 March 27th, 17:29

how did this guy get it on f4.8 on the very first try and never mind this comment "omg im so stupid, i thought he said f4.4"

DimmyDams

2008 March 29th, 08:05

I have to agree with some people here: this method is NOT needed. What you need to do is zoom in to the bright spot or dark spot of your frame, set and lock the exposure right there, zoom out, and record or adjust the exposure compensation a bit more and then record. So basically, a cellphone or other bright object that does not belong to the scene you are shooting should not be used. Just use objects from the scene you are going to record, zoomed-in, to lock exposure, and you are done. Or am I missing something?

The point of all this is to minimise and control the automatic gain which the camera kicks in if available light goes below a certain level.

Shooting under natural light indoors, say, the camera will gain-up and introduce grain. It could be that no amount of zooming in to the brightest object will stop this gain being introduced. So locking the exposure at this point will still have gain and noise.

Using another artificially introduced bright light in front of the camera, monitoring the aperture and locking exposure at a point where it is obvious no gain is being intoduced gives us the control we need.

I personally lock the exposure at an aperture a little above 1.8 to give me more range before gain kicks in.

The results using this 'trick' and shooting in 25p Tv mode are lovely and natural with no gain grain.

It's not under-exposing as such - just trying to stop the camera thinking every shot should be a full 1 volt!

Huge thanks to all who have contributed to this work-around.

madmaxmedia

2008 April 1st, 19:05

I don't know, I think I'm with Eugenia on this. I think the camera uses the same exposure adjustments whether it is on auto or manual- it will only introduce more gain if iris is wide open.

Reading Barry's article, at first glance it seemed that perhaps you could trick the Cinemode into never using slower than 1/48 shutter, which would have some advantages (ironically it could only do that by introducing gain, or purposely underexposing.) But in his list of readings, the apparent range of exposures all using 1/48 is probably limited, that's the only reason why he's not finding anything slower than 1/48 (in fact this is almost certain, if you look at the range of his exposures.) So as Eugenia speculates, the camera likely isn't behaving any differently in terms of when gain is turned on. It's not like there is some magical option after you've maxed out at 1.8 and try to lock at 1/48, if there's not enough light at that point then you either add gain, or underexpose.

All of this is fine, but you don't need a cell phone do check your lighting and possible gain. All you need is to half-press the photo button and check your exposure. If it's wide open, then adjust your exposure downward a bit and see if the iris closes. If not, then you're probably in gain territory. So you underexpose until the aperture goes up, then increase exposure one step because that's the best you can do without gain. Then you shoot away, and hopefully can fix in post.

For most beginners, you're probably best off leaving manual exposure alone. Whether you underexpose or introduce gain noise, you're going to try to fix in post, and I don't know if anyone knows if either is clearly superior. The far worse risk is forgetting to adjust your manual exposure lock after the lighting conditions change, and then shoot horribly underexposed or overexposed footage that absolutely cannot be fixed in post.

I do know for 100% sure, that nighttime driving video proves absolutely NOTHING. A camera tries to set exposure assuming everything is relatively grey (that's why a gray card is best way to set exposure). Most scenes are on average gray, but that nighttime driving scene is going to fool the camera into cranking up the exposure more than necessary. The second clip is simply underexposed compared to the first, it has nothing to do with using cell phones to trick the camera into not using gain. The exact same effect could be used by simply locking exposure and dialing it down- no cell phone needed.

What I am wondering (since I just got my HV20 and haven't experimented enough), is how decent is the built-in viewfinder in terms of gauging exposure level? Does anyone have a sense if it's hot or dark compared to actual footage, or perhaps its just totally unreliable? Anyone using the cell phone trick is going to need to accurately set exposure, most likely using the viewfinder as a reference.

Okay- one more thing I just discovered. Interestingly, if you are in aperture or shutter priority mode and half-press the photo button, the camera obeys your setting even for still pictures. So if like most users, you are locked at 1/48 shutter speed for a more filmlike look, the photo shutter speed won't change from that. So I think the quickest and easiest way to find out if GAIN is being introduced (when you are at maximum aperture, since this is not an issue otherwise) is to change your shutter speed to 1/24, then half-press photo button and check your exposure. If the aperture is still 1.8 (or whatever the max is at your zoom range), then almost assuredly you are introducing some gain at 1/48 shutter speed.

I think this is better than say zooming in and out to tweak aperture and then see effect on exposure, because if you are 1.8 totally wide, you can only increase aperture, not decrease aperture (which would be ideal in terms of checking for possible gain.)

madmaxmedia

2008 April 1st, 19:18

Sorry for the long post BTW.

In further thinking, the one area in which using the cell phone trick might be useful is if you are a real novice and don't have any sense yet of when there might not be sufficient light. You then use the cell phone trick to force the camera into only allowing a certain range of exposure (without gain.) Again though, you're probably then going to use the viewfinder to adjust the lighting, and I'm not certain that's a great idea.

But I think it is a more worthwile use of time for a budding videographer to just go out and shoot or check exposure in different lighting conditions. If you're in shutter priority at 1/48, play with the shutter and you'll quickly see if gain is being used by the camera. You'll also be able to pick a good object (say a gray card) and use the camera's autoexposure as the basis for your exposure, rather than relying on the viewfinder and totally manually setting exposure.

madmaxmedia

2008 April 1st, 19:23

Shooting under natural light indoors, say, the camera will gain-up and introduce grain. It could be that no amount of zooming in to the brightest object will stop this gain being introduced. So locking the exposure at this point will still have gain and noise.

That's not true at all. All you have to do is lock exposure and then adjust it down. The only difference is, would you rather start with an object in the actual scene and lighting that you're shooting, or start with a blank cell phone display?

So whether you use the cell phone trick or not, anyone can properly underexpose an image. ;)

madmaxmedia

2008 April 1st, 19:28

Here is another interesting thing (perhaps this has all been covered before and is only interesting to me?):

When you lock exposure, as you know the adjustment scale pops up. What is interesting is that the location of the 'zero point' varies depending on the lighting of the scene. If you are looking at a scene with moderate to bright light, the zero point starts in the middle. If you are in a dark scene, the zero point starts much closer to the right.

It might be possible to determine where the 'cutoff point' is in terms of gain. Most likely if you lock exposure and the zero point is right in the middle, the camera does not have gain turned on. But if the zero point starts shifted over to the right, then you likely have gain.

It then might be further possible to determine using the exposure scale how far you have to underexpose to cut out all the gain. It would be great if all you had to do was adjust exposure until the notch was in the middle. I haven't experimented enough to find out, perhaps this has been tried?

EDIT- Sorry, a correction. What is actually happening is that the zero point always starts in the middle. But the length of the line changes on either side, depending on the amount of light in the scene. So the net effect is the same- the camera is telling us roughly how much light is available. The question is whether that information is precise enough to tell us the exact cutoff at which gain is being added. I will play around with this more.

rkhanso

2008 April 2nd, 00:20

There was a recent post (Link (http://hv20.com/showthread.php?t=7525&highlight=double+click+aperture)) about "double-clicking" the exposure setting to get another full range of manual exposure to play with.

madmaxmedia

2008 April 2nd, 01:44

Hey, that's pretty good. It didn't occur to me to manually adjust exposure, then check for effect on aperture- that's a bit faster than tweaking the shutter speed, and accomplishes the same thing. The double-click thing is pretty tricky too. I would guess that if you can't get an image on your viewfinder after 22 steps, then it's way too dark anyhow.

Has anyone ever done a comprehensive comparison of the various gain levels and effect on exposure? The Canon CMOS in their digital cameras is reknowned for low noise levels at higher ISO (gain). I often just leave my Canon Digital Rebel at ISO 400 because noise compared to ISO 100 is about the same, even when viewing individual pixels at 100% on a computer monitor. That's 2 stops, which gets me a much faster shutter for photos. I don't know what the db equivalent is on the HV20.

In that post, the increments are at 1/4 stops for aperture (f/2.8, f/2.6, f/2.4, f/2.2, f/2), so I'm guessing the increments are the same for gain. If so, 1 stop is 4.5 db. Less noise is always better than no noise, but how noticeable is 3 or 4 steps of gain with the HV20?

If 1 stop is 4.5 db, then 27 db is 6 full stops. That's like going from ISO 100 to 6400 for a still camera, no wonder why there's so much noise at max gain. But I wouldn't imagine 3 or 4 steps making much of a difference, if that's equivalent to 1 stop. For the most part with still photography, underexposing 1 stop at ISO 100 and then bringing up levels in Photoshop is not going to deliver significantly different results than simply shooting at ISO 200 and doing a bit of noise reduction afterwards in Photoshop, etc. In general with photography the best advice would be to properly expose for the image, and then try to optimize it afterwards (there might be unique situations that call for different solutions.) Obviously it could be different here.

DimmyDams

2008 April 2nd, 04:10

For most beginners, you're probably best off leaving manual exposure alone. Whether you underexpose or introduce gain noise, you're going to try to fix in post, and I don't know if anyone knows if either is clearly superior. The far worse risk is forgetting to adjust your manual exposure lock after the lighting conditions change, and then shoot horribly underexposed or overexposed footage that absolutely cannot be fixed in post.

I do know for 100% sure, that nighttime driving video proves absolutely NOTHING. A camera tries to set exposure assuming everything is relatively grey (that's why a gray card is best way to set exposure). Most scenes are on average gray, but that nighttime driving scene is going to fool the camera into cranking up the exposure more than necessary. The second clip is simply underexposed compared to the first, it has nothing to do with using cell phones to trick the camera into not using gain. The exact same effect could be used by simply locking exposure and dialing it down- no cell phone needed.

I think to advise 'most beginners' not to try manual exposure control is wrong.

Surely its preferable to encouraging learning, particularly when the results can be so good.

To state that the night-time driving footage 'proves absolutely nothing' is wrong too. It proves that manual control of the exposure can produce superior results and that this domestic camera can be tamed in the way it introduces terrible noise when gaining up under low light.

jabloomf1230

2008 April 2nd, 11:23

Has anyone ever done a comprehensive comparison of the various gain levels and effect on exposure? The Canon CMOS in their digital cameras is renowned for low noise levels at higher ISO (gain). I often just leave my Canon Digital Rebel at ISO 400 because noise compared to ISO 100 is about the same, even when viewing individual pixels at 100% on a computer monitor. That's 2 stops, which gets me a much faster shutter for photos. I don't know what the db equivalent is on the HV20.

I think you've hit on the crux of this issue. Digital Photography Review has a standard test that use in their camera testing suite. Here's an example with the Canon 40D:

http://www.dpreview.com/reviews/canoneos40d/page18.asp

Until someone does (or finds) a similar test with the HV20/30, it is difficult to tell whether too much gain is worse than underexposure. The former makes the video grainy/spotty. The latter makes the picture darker. It is easier to fix the latter in post, but just saying that 0 db gain is an absolute cutoff is probably not correct either. As you correctly state, the Canon CMOS chip does an excellent job with its electronic gain.

madmaxmedia

2008 April 2nd, 12:05

You are right, I'm sorry I was unclear.

It is very good for a beginner to learn manual exposure, and exposure in general.

I think doing it this particular way is not so good, I think people are getting certain impressions from this that are simply not the case. The night time driving clip is a perfect example. It's not the 'trick' that eliminates the gain, all you needed to do was recognize that A) lighting is not good, and B) the road is dark and thus will likely fool the camera's autoexposure. Knowing that, you can selectively dial down exposure a few steps, and then shoot and get the exact same results.

The cell phone 'trick' is not actually a trick, referring to it as a 'trick' gives people the wrong impression about it. There's no magic or special bypass that you get with it. If someone really wants to learn how to shoot good video, I think it is worth it to take a small amount of time and learn the basics of exposure, instead of figuring out the proper cell phone display brightness and then using that method. In the mid to long run you will end up with a much better grasp of exposure in general. There will be other circumstances where autoexposure will likely give better results than using this trick.

The original article by Barry was very informative and useful, in that he was able to find out the camera's settings for various levels of exposure. We were able to confirm that gain is the method of last resort by the camera. But now that we know that, there's no reason to artificially limit the exposure range, in the mid to long run it's a crutch that holds you back. Even Barry states in his article that the easy way is to simply get a mini-SD card so you can check exposure level, and that the hard way is to use a bright set point (such as a cell phone screen) and then adjust from that.

I'm also not convinced that adjusting exposure via the viewfinder is very good method. When light levels are really low, then using the cell phone method there's no decision to make, you're simply going to go down as far as possible. But what about when light is so-so? In these cases a gray card will be far more useful and informative than locking exposure against a cell phone screen, being that it only takes 10 seconds to find out if gain is being applied in any given lighting situation anyway. You'll be able to determine the proper exposure for a scene, and then can selectively dial it down if gain is being applied.

I am sorry if I am being argumentative, I think all of this discussion is ultimately for the good no matter how you do it. I'm not saying everyone should or must do it one way or the other, I'm just saying there are some basic concepts of exposure that negate the need for any 'tricks', and that using the 'cell phone trick' can impede one from learning these basic concepts.

Cheers
steve

I think to advise 'most beginners' not to try manual exposure control is wrong.

Surely its preferable to encouraging learning, particularly when the results can be so good.

To state that the night-time driving footage 'proves absolutely nothing' is wrong too. It proves that manual control of the exposure can produce superior results and that this domestic camera can be tamed in the way it introduces terrible noise when gaining up under low light.

madmaxmedia

2008 April 2nd, 12:22

Yes, since even 0 db gain is an arbitrary set point. It doesn't mean absolutely 'no gain', the zero is a relative term.

For still cameras, most people consider ISO 100 to be the equivalent of zero gain. But many cameras go down to ISO 50 or even ISO 25 IIRC. But all these numbers are arbitrary set points as well, chosen based on rough equivalence with film (still or motion.)

I'm still learning the ins and outs of the camera and getting footage into my storage-deprived MacBook. But I have a pretty good handle on determining exposure and gain now, so will try to do some comparison shots with various gain levels. I'll post some screens if I do.

The one thing about the night time clip is that it is most certainly an apples to oranges comparison, because due to the particular scene he didn't have to lighten the scene in post. Another great test would be to shoot a relatively 'normal' scene in so-so light, with various levels of gain/underexposure, then try to correct BOTH in post. There may not be a big difference between the 2. Certainly with still cameras there wouldn't be. If the camera is applying all 18 steps of gain while properly exposing a scene, the shot is going to look relatively crappy whether you let the camera apply all the gain, or you underexpose by 18 steps and try to bring it up in post.

I think in many low-light shots, people are shooting a subject that is actually lit to a decent degree, but against a dark background (say a table lamp or even a candle close to the subject.) In those cases the camera is going to crank up the gain to brighten up the whole frame, so an auto-exposed shot is not going to be optimal. The cell phone trick sorta helps, in that it doesn't let the camera crank up exposure very far. That is fine, but it's not so good if the user gets the wrong impression about what is actually happening- there are actually 2 variables involved, not just gain.

Anything that gets the user more involved with the camera is a good thing. But I do think it's also important that everyone is clear on what is actually happening with the cell phone method, what the limitations are, and that learning how to expose without it is A) not that difficult, and B) will give you more flexibility and provide better results overall.

I think you've hit on the crux of this issue. Digital Photography Review has a standard test that use in their camera testing suite. Here's an example with the Canon 40D:

http://www.dpreview.com/reviews/canoneos40d/page18.asp

Until someone does (or finds) a similar test with the HV20/30, it is difficult to tell whether too much gain is worse than underexposure. The former makes the video grainy/spotty. The latter makes the picture darker. It is easier to fix the latter in post, but just saying that 0 db gain is an absolute cutoff is probably not correct either. As you correctly state, the Canon CMOS chip does an excellent job with its electronic gain.

DimmyDams

2008 April 2nd, 13:39

Absolutely...

I know this isn't by any means an extensive test but I've attached a couple of files.

One taken with the camera on auto and one taken with zero gain then gained up in post. I know which I prefer...

jabloomf1230

2008 April 2nd, 16:31

Could you run the "Auto" version with HDVdataMon, and write down the gain for that scene, so that we could have a better idea of the actual gain? I think that your comparison represents the typical results with the HV20 auto mode in low light. But it still doesn't get at the issue of how much gain is too much. Obviously +27 db gain is going to give you a pretty blotchy result. But is +1.5 db or +3 db still okay for most applications? The less fiddling that you have to do in post, the better.

nzo

2008 April 2nd, 18:47

Dimmydams...for us beginners please share which one you prefer. :)

DimmyDams

2008 April 3rd, 03:18

:hv20-smilie03:

bimpatiens

2008 April 3rd, 08:24

Pointing at a light seems to be a bit of a red herring .. the easiest method is just set the shutter (1/48 on mine) then point at a brighter thing in the scene (the white fireplace in my case)

If you click on manual exposure and then reduce exposure to -11 and it's still reading 1.8 you know that you are probably adding gain no matter what (or will have a VERY dark scene). If increasing gain to +11 you still have an f stop number greater than 1.8 you know the scene is light and you won't add gain.

At least that's my 2 cents from my playing.

I like the simplicity and directness of this approach. Do you have some sample shots to share?

madmaxmedia

2008 April 3rd, 10:49

Hi Dimmydams,

Thanks for posting, this is a good start.

As the other poster says, it's important to know what level of gain was applied- there are 18 steps to work with.

The other thing is that noise reduction should be applied to the auto-exposed image, thus both images are corrected in post. If you only correct 1 image then it is not really a 'fair' trial.

If noise reduction is applied, then I suspect the first few steps of gain (out of 18 total) will be pretty close to turning gain off and bringing up levels in post.

Just to be complicated ;), a final factor in this subject is how much dark detail is lost when underexposing significantly. I don't think it matters too much here (vs. still photography), but if you underexpose too much you will start to lose detail that cannot be recovered in post.

Thanks,
Steve

madmaxmedia

2008 April 3rd, 10:51

I like the simplicity and directness of this approach. Do you have some sample shots to share?

Hi bim,

I can say with almost 100% certainty that either methods will produce the exact same results. In both cases you are dialing down exposure until no gain is being used by the camera.

Ian-T

2008 April 3rd, 12:11

Yes, since even 0 db gain is an arbitrary set point. It doesn't mean absolutely 'no gain', the zero is a relative term.

It's funny you say this. I recently thought the same thing. Usually, for me at least, the way I can tell gain was added to the picture is more in post work. What I mean is in post I would add gain to my footage( being that it's sometimes way too dark) and notice certain artifacting popping up in my footage. This was footage that was shot at 0db gain (indoors @ 24p - 1/48 - f 1.8...just above f 2.0 ). Usually, when there is truly no gain added durinig filming I can push the gain in post with no real artifacts....but not everytime. Maybe, to truly assure you have no gain in the picture, we need to shoot for f2.0 instead of the f1.8 we have been pressing.

When I shoot with no gain....I don't have this problem. You can not tell that gain was added because the picture comes out so dark sometimes that it seems to hide the artifacts.....until you push it in post.

Rumpelgeist

2008 April 3rd, 12:51

Why people cannot read the thread from the beginning before posting? This discussion is going in circles. One f-stop is 6 dB, one EV step is 1/4 f-stop, which means one click of gain is 1.5 dB. End of story.

Ian-T

2008 April 3rd, 13:22

madmaxmedia

2008 April 3rd, 13:28

It's funny you say this. I recently thought the same thing. Usually, for me at least, the way I can tell gain was added to the picture is more in post work. What I mean is in post I would add gain to my footage( being that it's sometimes way too dark) and notice certain artifacting popping up in my footage. This was footage that was shot at 0db gain (indoors @ 24p - 1/48 - f 1.8...just above f 2.0 ). Usually, when there is truly no gain added durinig filming I can push the gain in post with no real artifacts....but not everytime. Maybe, to truly assure you have no gain in the picture, we need to shoot for f2.0 instead of the f1.8 we have been pressing.

I wouldn't guess this is necessary (shooting for f2), since it is possible to determine how much gain is being added, and thus how much to dial down exposure if you want to totally eliminate gain.

The differences you see in footage might also be due to the particular scenes you are shooting. With still digital cameras, different types of scenes tend to show more noise than others, I imagine the same holds true here.

When I shoot with no gain....I don't have this problem. You can not tell that gain was added because the picture comes out so dark sometimes that it seems to hide the artifacts.....until you push it in post.

I think this is somewhat of a factor with the example at the top of the page. The zero gain image was brought up in post, but not enough to match the light levels of the auto-exposure shot. That may have been the desired look he was going for (the darker look works there due to the highlights on the chess piece), but it gets in the way of a direct comparison of noise between the 2.

madmaxmedia

2008 April 3rd, 13:50

Aramis, I'm not sure who you are referring to but if you think this discussion is going in circles then you could simply just exclude yourself from it. I understand that these settings are what was figured out by many folks here and in other forums...but honestly...no one really knows what is going on inside this camera....so to me it's just guessing. I know what the numbers say and where gain is supposed to kick in but I am starting to rely more on what my eyes see than the numbers.

I thought he was talking about me, since I made a long post regarding gain and f-stops. But I don't know. I don't see any going around circles in any case either...

As I mentioned above when i'm in TV mode and filming indoors sometimes...I can set the camera to the optimal settings (where there should not be any noise or gain present) but the picture, in many cases, can be too dark. So when I lift the gain in post it reveals noise in the picture...why is that? I can actually get the same type of shot if I were to add 1.5 or 3db of gain while shooting (but wouldn't that defeat the purpose of using the light trick). It's as if the darker picture is hiding the noise "that was recorded already." Where did it come from?

I think what might be happening is that normally shots with lots of detail, contrast, different colors, etc. (most normal scenes) are going to 'hide' any noise inherent to the sensor/camcorder. Zero gain does not literally mean no gain whatsoever, it's a relative term. And so no image is going to be perfect or 100% free from noise too (although the HV20 does a great job under a wide range of lighting conditions.)

If you shoot a dark scene but have highlights on the subject, then the image will subjectively look good without too much gain added (such as the chess pieces shot, it looks very nice.) OTOH if you're shooting a scene where everything is in the shadows, it's not going to look as good because you'll be cranking up gain (either while shooting or in post), to bring out a dark, low contrast subject.

I've mentioned this months ago...but I have resorted to allowing some gain into my picture (especially when the scene is too dark). I mentioned "some gain is not that bad." I have Neat Video and it cleans up the image perfectly....everytime. You can't allow a lot of gain however because no matter what you use in post...it will still be a muddy picture.

Is Neat Video made by the same company as Neat Image? I assume so, their software works very well for still cameras.

I agree that some level of gain is not bad. I guess the question is how much is more or less acceptable and won't make a signficant difference in overall image quality (with or without post-noise reduction.) That is a different issue than determining if the camera's autoexposure is being tricked by a very dark scene, in which the camera is going to overexpose and create additional problems. A slightly different but related set of problems can also occur if you defeat the camera's autoexposure and always reduce exposure more than necessary (I'm still not sure how good using the viewfinder to manually set exposure is, when you're using the cell phone method.)

Since most people here seem to be more concerned about a nice look than maximum detail, generally underexposing and then bringing up in post doesn't seem like a big problem. Especially if you are able to make sure there's at least some decent, contrasty light on the subject even if the whole scene is dark. I imagine even a candle light could produce a very nice mood-type image, if it was close to the subject.

Ian-T

2008 April 3rd, 14:02

Since most people here seem to be more concerned about a nice look than maximum detail, generally underexposing and then bringing up in post doesn't seem like a big problem. Especially if you are able to make sure there's at least some decent, contrasty light on the subject even if the whole scene is dark. I imagine even a candle light could produce a very nice mood-type image, if it was close to the subject.This staement is very true. There are lots of examples in this forum with videos and pictures like that. Here (http://www.hv20.com/showthread.php?t=7492&page=3&highlight=lou+van) at the bottom of the page is a perfect example posted today by Lou Van Wijhe.

DimmyDams

2008 April 3rd, 14:27

Hi

Yes I was going for the more natural darker look which I preferred to the camera's choice in auto.

But gaining up further in post still produces better results than the 'auto mode'.

Incidentally gain being introduced by the camera in auto mode was 21dB in this case.

Let me say at this point...I am certainly not saying always try to shoot with no gain...some shots will be unrecoverable in post due to black crushing if a scene is too dark for zero gain.

I personally adapt the 'trick' so that I have a reasonable range of additional gain at my disposal. I lock at 1/50 f2.2 which gives me a range of gain up to 12dB. And yes I use an old mobile phone bang on the lens to give me this very quickly.

Gain introduced by the camera is perfectly acceptable of course, so long as it is controlled to stop the camera thinking (in auto mode) everything has to be a full-on 1 volt.

Cine mode for example seems to cap the gain at 9dB producing very acceptable results in low light (albeit with 1/25 shutter).

But as to shooting in cine mode - that's another debate! :)

Ian-T

2008 April 3rd, 14:51

I know it's been mentioned before, but the whole point of this "light-trick" is to give us more control of the in-cam gain. That's obvious...and I will agree with Aramis in this regards of us going in circles. But outside of that I think it's good for folks to know "why" this is important....and that there are sometimes acceptable levels of gain....and ways around grain in the final picture. Maybe we should put together a lighting techniques tutorial...not only with your basic three point lighting etc., but with different lighting conditions and how you can get the best picture (with the HV20/30 of course.....it might be different with other cams that have a wider aperture etc.)....just a thought.

Personally I don't use the light trick...unless I'm using cinemode. That might be a whole other discussion (which I posted here (http://www.hv20.com/showthread.php?t=8582&highlight=Ian-T) about) .

jabloomf1230

2008 April 3rd, 23:34

But gaining up further in post still produces better results than the 'auto mode'.

Incidentally gain being introduced by the camera in auto mode was 21dB in this case.

Thanks. A couple more thoughts (and I hope they are linear :hv20-smilie15:). In my experience (everyone's will differ), roughly about 4.5 to 6 db (3-4 steps) of gain past the f1.8/0 db gain setting still gives you decent low light results. In your "Auto" example above, 21 db of gain is pretty obviously grainy.

The whole argument as to whether you should either underexpose with 0 db gain or allow some small amount of gain, hinges on how strong the signal is to the noise. In simple terms, graininess is a kind of random unpredictable noise that is not evenly spread over a whole frame. It also affects some colors more than others. It's a kind of problem that's not easy to correct in post. Again, in simple terms, underexposing is also bringing up the "noise" in relation to the signal, but in this case, the noise is more uniformly distributed throughout each frame.

If fixing underexposure in post was really so efficient and effortless, why wouldn't everybody always underexpose low light shots? After all, you could increase your DOF by using a narrower f stop. Or you could use a higher shutter speed to cut down on motion blur. But the latter is the good reason for controlling gain. In 24p, you want to maintain a shutter speed of 1/48.

Someone said it above; to some extent, the proper solution to the low light problem is to improve the lighting (duhh!). That is not always possible. But if it is, it is an approach that requires a lot less work.

Steve Kahn

2008 April 4th, 16:49

Has anyone ever done a comprehensive comparison of the various gain levels and effect on exposure? The Canon CMOS in their digital cameras is reknowned for low noise levels at higher ISO (gain). I often just leave my Canon Digital Rebel at ISO 400 because noise compared to ISO 100 is about the same, even when viewing individual pixels at 100% on a computer monitor. That's 2 stops, which gets me a much faster shutter for photos. I don't know what the db equivalent is on the HV20.

In that post, the increments are at 1/4 stops for aperture (f/2.8, f/2.6, f/2.4, f/2.2, f/2), so I'm guessing the increments are the same for gain. If so, 1 stop is 4.5 db. Less noise is always better than no noise, but how noticeable is 3 or 4 steps of gain with the HV20?

If 1 stop is 4.5 db, then 27 db is 6 full stops. That's like going from ISO 100 to 6400 for a still camera, no wonder why there's so much noise at max gain. But I wouldn't imagine 3 or 4 steps making much of a difference, if that's equivalent to 1 stop.
That is a very good point.

Another point is that it is best to expose to the right of the histogram - just before clipping and then if the picture is too blown out to correct in post. The reason for this is due to the intrinsic bit nature of digital processing, that is MOST of the information recorded is at the high end of the spectrum. If you constantly underexpose you are losing information and will have a lot of noise in darker parts of the spectrum. (I would guess much less noise than you would get by turning up the gain a few dbs)

I have seen many people recommending zebras to be set at 70 but that would lead to the problems I talked about above.

Braceface

2008 April 4th, 20:06

That is a very good point.

Another point is that it is best to expose to the right of the histogram - just before clipping and then if the picture is too blown out to correct in post. The reason for this is due to the intrinsic bit nature of digital processing, that is MOST of the information recorded is at the high end of the spectrum. If you constantly underexpose you are losing information and will have a lot of noise in darker parts of the spectrum. (I would guess much less noise than you would get by turning up the gain a few dbs)

I have seen many people recommending zebras to be set at 70 but that would lead to the problems I talked about above.

I like the Lytecap©. It is soooo much faster to lock exposure at the optimal settings with the filimic 1/48th shutter. The thing about shooting low light scenes is that it is sort of a bad way of explaining the situation enherant with low light. Contrast is the real issue. If you have enough contrast then you will have no problem. In a dark or dim room, everything looks bland. You need light in your shot from " somewhere " or the shot will look bad.
The stronger the light is on the subject, the darker things in the background will look. So you can actually create a dark scene in a light room if you have the right contrast. You can have minimal light and still have a well lit look to your subject, as long as the light is strong enough to give enough contrast around the frame. Otherwise the subject blends in and everything is flat. So it's not the amount of light alone, but a whole hodge-podge of things. When I shoot parties, i don't bring my hmi lights and blind everybody. I will however get people to turn lights AROUND the subject off so the light nearest the subject LOOKS brighter by comparison. Basically I try to avoid lighting the area more than the focus of the shot, wether it means adding light to the subject, or taking light away from the rest of the frame.
But saying all of this, I still use the LYTECAP© and get my camera to act more like a movie camera, than a prosumer video camera. I like having the parameters stay stable and from that point I can master the camera without fighting internal camera operations that don't ask me what I want. I'd rather have a stupid camera that doesn't try to act smart than a smart camera that constantly acts stupid.

jabloomf1230

2008 April 6th, 00:30

Just to examine the gain issue a little further, here is a screen capture from Vegas 8 Pro. The right half is the original frame, taken at 1/60, f1.8 and +21 db gain in "Auto" mode. The left half is processed with the excellent NeatVideo plug-in (which is available for most NLEs). It is possible to remove the graininess introduced by the HV20/30's gain, but what you can also see is that the real texture of the carpet is somewhat lost within the processed half of the frame. With a little tinkering with NV, the results can be improved a bit, but there is a law of diminishing returns, as you spend more and more time in post.

madmaxmedia

2008 April 6th, 02:32

Thanks for the post. Yeah, typically you can use heavy noise reduction to make an image look better, but at the expense of detail.

Although conversely, I wonder how much detail you lose by shooting underexposed by 14 steps (3.5 stops)?

Just to examine the gain issue a little further, here is a screen capture from Vegas 8 Pro. The right half is the original frame, taken at 1/60, f1.8 and +21 db gain in "Auto" mode. The left half is processed with the excellent NeatVideo plug-in (which is available for most NLEs). It is possible to remove the graininess introduced by the HV20/30's gain, but what you can also see is that the real texture of the carpet is somewhat lost within the processed half of the frame. With a little tinkering with NV, the results can be improved a bit, but there is a law of diminishing returns, as you spend more and more time in post.

Arla

2008 April 14th, 13:33

I like the simplicity and directness of this approach. Do you have some sample shots to share?

Not yet, I'll try to take a few tonight... haven't really been playing much recently, too much baby preparation :hv20-smilie81:

Arla

2008 April 16th, 00:20

Okay, got two screen captures, I did both in where I could get gain but could zero the gain without having to do the double click trick or anything like that.

Anyway, pictures (not sure how to get better thumbnails yet, will have to keep looking around here, these are the first pictures I've tried)

http://lh6.ggpht.com/James.Duerr/SAV9D5EpWuI/AAAAAAAAAGY/YOIVKdZ2W4g/s400/Auto.JPG

http://lh5.ggpht.com/James.Duerr/SAV9LpEpWvI/AAAAAAAAAGg/3ZPplRn1cHk/s400/NoGain.jpg

Adler

2008 April 28th, 13:28

Ok, So how would you get rid of gain in post, if your stuck with grainy footage? ( preferably Premiere Pro CS3 or After effects)

jabloomf1230

2008 April 28th, 15:47

NeatVideo (http://www.neatvideo.com/)

It's a noise and grain reduction package for various NLEs. It does a pretty good job for the price, but don't expect miracles. Also, if you use the HV20.com search function, you will find a few threads about reducing graininess in post.

Flint Loveless

2008 May 7th, 18:15

Does this lock exposure trick work for the HV30? Has anyone confirmed it?

Rumpelgeist

2008 May 7th, 19:25

Does this lock exposure trick work for the HV30? Has anyone confirmed it?
It is not a "trick". Yes, it works.

Flint Loveless

2008 May 8th, 02:49

Isn't it a trick considering it isn't an option on the camera? Let's call it an Easter Egg of the HV series.

I can't wait to get mine!

bimpatiens

2008 May 8th, 05:27

without having to do the double click trick or anything like that.

Nice shots (like the second one better!). Just for grins - how were these done again?

cazz77

2008 May 17th, 16:27

That's a pretty accurate analogy. Gain is effectively making the sensor more sensitive to light in the same way that a faster film speed would. The downside, in both cases, is that you sacrifice image quality.

By setting the shutter and aperture manually in the way the tutorial demonstrates, you're setting up the camera to avoid the addition of 'gain' and therefore you are inherently improving the image. You're making a decision about shutter speed, aperture and overall exposure and you're locking in these settings. That being said, you won't necessarily be able to shoot in any random situation you might happen upon.

In your example of walking from one room to the next, there simply might not be enough light to get an acceptably bright image when you've locked your shutter speed and f-stop at whatever it's been locked to. In that case, you'll either need to adjust your shutter speed, or open up your aperture. If you can't do either (because you're already shooting wide open and you're at the slowest acceptable shutter speed available) then your only option is to either live with an underexposed image or unlock things and allow the camera to add gain.

Yeah but Dude usind the exposure control whiel going trough moderate light change can be adjusted with a little practice since consumer camera buttons haperm to be a tad bit too small LoL....I recommen this for Indie film making were you have absolute control...Now if your a novice at a nascar race I wouldnt sggest it for obvious reasons But needless to say IS YES WHILE RECORDING YOU CAN CHANGE THE APATURE FOR ACCURATE EXPOSURE.:)

Flint Loveless

2008 May 21st, 20:10

Can you do this without an SD/Memory Card? I'm pretty sure I heard that somewhere and I can't seem to find that info so I'm asking.

Anyone know?

madmaxmedia

2008 May 21st, 21:27

It's a lot easier to use a memory card, it allows you to check exposure settings at any time really quickly by half-pressing the photo button.

They're under $10, really nothing compared to the cost of the camera.

Rumpelgeist

2008 May 21st, 22:26

Can you do this without an SD/Memory Card? I'm pretty sure I heard that somewhere and I can't seem to find that info so I'm asking.
Do what exactly? Without a card, the camera does NOT report exposure settings when you press Photo button.

Flint Loveless

2008 May 22nd, 02:56

That was the answer I was looking for... Thanks!

Arla

2008 May 22nd, 11:29

Nice shots (like the second one better!). Just for grins - how were these done again?

Essentially I just stuck the camera on a tripod (or equivalent thereof) put it in TV mode, set shutter to 1/48, for the first I just took video (since I wanted to get a frame capture from video, rather than a photo) for the second one I used the exposure lock feature and photo button to check what the aperture was (if I'm recalling the right terms) kept lowering the exposure until the aperture reported was 2.0, and the clicked it back up one (to 1.8) this is the point that I know the aperture is wide open without having added any (more?) gain.

Video screen grabs were just done in Vegas Pro 8, nothing fancy really just grabbing a screen shot from the video.

cazz77

2008 May 29th, 02:14

this is a tutorial i made a few days ago on how to control the aperture and gain on the HV20. i had been up for about 20 hours so you can tell I'm a little muddled and tired. so if someone else want to make a better one that's more clear, please do so :)

this is the PAL version, so it's basically exactly the same but the NTSC version would have different shutter speeds.

you need a miniSD card in your camera for this to work.

http://hv20.info/yopu/hv20aperturecontrol.mov

mirror - http://www.megaupload.com/?d=JNDHJMN5

i prefer to use cine mode because you get the extra shutter speeds if you need them. you get 25, 29, 33 ,40 and 50 where as you only get 25 and 50 in TV mode.

Great video ,seriously But once you lock the exposure(In bright light)and have control over the shutter/aperature no matter how much you open the apature it seems dark(In the video)regardless?So what are you realy controlling? IM confused,just bought a hv30 let me know how to control light after you set the exposure in the bright light,thanks in advance!

-Charlie

Gymnut808

2008 May 29th, 02:26

Can you do this without an SD/Memory Card? I'm pretty sure I heard that somewhere and I can't seem to find that info so I'm asking.

Anyone know?

http://dvxuser.com/jason/hv20/

About 1/4 of the way down:

But what if you don’t have the mini-SD card (or, if you just like doing things the hard way?) Can you still lock the exposure exactly where you want it to be? Yes, and it’s easy once you know how, but it requires an absolutely controlled set of light entering the HV20’s lens. The easiest way to force this circumstance is to completely block the HV20’s lens so that no light enters the camera whatsoever. An external lens cap would be ideal for this purpose, for example. Start out by zooming out to 100% wide angle; you want it as wide as possible so you have a consistent iris to open up to (the further you zoom in, the smaller your maximum-open iris can be; start at maximum wide angle to get the fullest range of iris settings). If you set the camera in Shutter Priority (“Tv”) mode and set the shutter speed to 1/48, and then cap the lens (so that there’s no light entering the camera at all) the autoexposure system will force the camera to select a completely wide-open iris (f/1.8) and maximum electronic gain (27dB). So cap the lens, then lock the exposure, and you’ll see that you have an exposure range of –11 to +0. (Note, this is one of those cases where you don’t get the full –11 to +11 range). The reason is, at “0”, the HV20’s already maxxed out – it’s got the iris wide open and the gain pumped up to a startling 27dB. Finally we have a way to guarantee what our exposure is for all three parameters!

Doable, but as pointed out earlier, does not give you aperture and shutterspeed settings. 1GB miniSD cards can be had for under $10.

gramdion

2008 July 9th, 01:52

colonelpanic

2008 July 9th, 03:36

I've tried the manual control of shutterspeed, aperture and gain. It works. I was just wondering about zoom. Let's assume that i'm using the widest zoom (1X). I have adjusted the settings so I have no gain and appropriate shutterspeed / aperture settings. Then I zoom in to 5X. Now the light hitting the CCD has diminished to a fraction of the original. Does HV20 take this into consideration and how? Or is it so that the picture only changes to darker? What i'm specifically asking i guess is that does it propably add gain to cope with the changed lighting enviroment?

This may have been discussed before but as at least two people (including myself) must have missed it, I chime in and say 'this is a good question'. ;) From my tests I've noticed the following:
The aperture closes as you zoom in - which is no news as most sub $1000 fast zoom lenses behave this way. If you keep the exposure locked it should not add any gain, so the picture should get darker by keeping all the other parametres constant. The weird thing I've noticed is that the picture does also get grainy instead of 'just' darker. (I would expect really dark parts of the frame become evenly black, instead of black with coloured specks.) It seems to me that your guess is correct.
Does anyone have an explanation for that? Better still, a solution?

destruct007

2008 July 9th, 23:02

after half reading and watching the video I thought I knew what this trick was all about. I finally got the card after reading that the firmware is probably going to be hacked with a sd card... well damn this technique is great! I thought you had to point the camera at a light and lock the exposure, never realizing that it was always at a higher f stop.

as for the question above, it does add gain when you zoom try zooming in then redoing the video suggestion to figure out when the gain is applied. in this case you will be subtracting from your locked exposure. keep subtracting until the aperture changes to a higher number and then go back one to where you are at the lowest 2.8. that will be your zoomed in no gain level.

fleants

2008 July 16th, 22:47

I got the shutter speed to vary in TV, like in the vid, but I just dont know how to do it in cine mode.:hv20-smilie51: it would be very helpful, considering it is my favorite setting.

sfdex

2008 July 17th, 18:46

Unfortunately the cinemode doesn't allow you to control the shutter, aperture and gain. You can influence exposure with the plus/minus exposure control, but the rest stays automatic. Kind of a bummer. You can simulate the gamma and tonality changes that Cinemode imparts to your footage in post production, so eventually you could get the same basic look, but it's not as easy.

That's one of the disadvantages to using a consumer camera and trying to get it to go "full manual."

:/

Humourwriter

2008 July 21st, 22:29

Not sure it's been mentioned already in this thread, but there's a gizmo called the LyteCap that may make things a bit easier.

http://www.lytecap.com/multimedia.htm

Bill.

Zintoit

2008 August 3rd, 15:38

keep subtracting until the aperture changes to a higher number and then go back one to where you are at the lowest 2.8. that will be your zoomed in no gain level.

I'm glad you mentioned this.

Locking the exposure to 4.8 to achieve a 1.8f aperture setting (as someone mentioned in a previous post) flat-out doesn't work: because there is gain (meaning grain = noise) at 1.8f. Today I will record at 2.6f, 2.8f and 3.2f to find the true no gain point.

Also, for those who have shot grainy footage Neat Video has software out that can help - if even moderately. Here, a trade off occurs the more grain the software removes the more it softens (read that: fuzzes) your image.

http://www.neatvideo.com/

All in all, I believe the best solution here is to fix the aperture at a no-gain level and increase lighting where possible.

There is another thread addressing the issue of a firmware upgrade to eliminate gain but I just checked it out and see no progress there.. also in that they preclude the hv20 rules out a firmware upgrade as an option to eliminating gain in the hv20.

Zintoit

2008 August 4th, 22:35

Yesterday I tested the point the cam at a light source and lock the exposure trick on an indoor take using standard lightbulbs and still get "grain" and the "moving pixels effect" in low light areas. Ugh.. this is exhasperating.

Workflow:
Vegas to capture
hv20pulldown.exe: pulldown / .m2t to avi conversion
Super to compress to mp4

Rumpelgeist

2008 August 4th, 22:42

Yesterday I tested the point the cam at a light source and lock the exposure trick on an indoor take using standard lightbulbs and still get "grain" and the "moving pixels effect" in low light areas.
You understand that simply locking exposure when pointed to a bulb is not enough to prevent gain, do you?

kvibe

2008 August 14th, 16:45

Hi,

I've gone through a few topics and went through this whole thread. I understand the whole exposure lock / aperture settings / and so forth.......However, what I don't understand is if someone has a 35mm Adapter where you need to zoom in a little more to get to the focusing screen, how do you go about that with regards to getting the gain to 0? Do you go through the process before you add the 35mm Adapter and Lens, or do you do that afterwards?

Common sense says to do it afterwards, but how if everyone is mentioning that you need to be fully zoomed out. How do you get appropriate lighting exposure with the cell phone or light if you are zoomed out with the lens and adapter attached?

Also when lock the exposure, do you lock it while the camera is pointing at the bright light or you do it immediately after you remove the bright light?

Rumpelgeist

2008 August 14th, 17:09

The HV has lens with variable speed, f/1.8 on the wide end and f/3.0 on the tele end. If you want quick and simple solution, then always make sure that your aperture is narrower than f/3.0, this guarantees no gain.

http://www.elurauser.com/articles/manual_mode_aperture_table_hv20.gif

If you want as wide aperture as possible in current situation, you need to play with EXP slider and watch it when it starts changing its value. Say, you are in the mid-zoom, you locked exposure and current aperture is f/2.4. Now decrease it until it gets f/2.6, then make one step back to f/2.4, this is the point where aperture is the widest and no gain applied. This "trick" always work, no matter what your zoom is. Should I call it "EV fiddle" trick?

This is explained in my article: http://www.elurauser.com/articles/manual_mode.jsp

Sure you lock the camera while pointing to the source, otherwise it will readjust itself. Heck, the whole point of pointing (no pun intended) to the light source is to shift EV scale into narrower apertures and/or lower gain.

Paul Tarlevs

2008 August 24th, 11:02

this is a tutorial i made a few days ago on how to control the aperture and gain on the HV20. i had been up for about 20 hours so you can tell I'm a little muddled and tired. so if someone else want to make a better one that's more clear, please do so :)

this is the PAL version, so it's basically exactly the same but the NTSC version would have different shutter speeds.

you need a miniSD card in your camera for this to work.

http://hv20.info/yopu/hv20aperturecontrol.mov

mirror - http://www.megaupload.com/?d=JNDHJMN5

i prefer to use cine mode because you get the extra shutter speeds if you need them. you get 25, 29, 33 ,40 and 50 where as you only get 25 and 50 in TV mode.

Hmmmm thats weird...my hv30 doesn't have 50 shutter...why?

CycleWriter

2008 August 24th, 12:20

Hmmmm thats weird...my hv30 doesn't have 50 shutter...why?

Because you have the NTSC version. The post you quoted is referring to the PAL version.

Paul Tarlevs

2008 August 24th, 15:53

Because you have the NTSC version. The post you quoted is referring to the PAL version.

Thank you. I got it now

Paul Tarlevs

2008 August 25th, 10:44

Is it possible to do this in cinemode? Would it be better to do this in cinemode or tv mode? After this trick what would look more like film?

If I were to use cinemode, I would also need to change the shutter speed to what? 1/48 or 1/24?

Whats the best shutter speed to use for more of a film look?

Those are my three questions.

Thanks.

Rumpelgeist

2008 August 25th, 13:16

Is it possible to do this in cinemode? Would it be better to do this in cinemode or tv mode?
What do you mean by "this"? You can control overall exposure in terms of brighter/darker but you cannot control individual settings like shutter speed or aperture. On the other hand you can always check what your current settings are using the Photo button. Then use this table to see where you are at:

http://www.elurauser.com/articles/canon_cinemode_table.jsp

Down the table are values achieved when you click EXP slider to the left, up the table go values when you click EXP slider to the right.

After this trick what would look more like film?
Will your video look like film or not does not depend on this "trick". Using the Photo button is just means to assess your current exposure settings, not to switch the camera into some magic mode.

If I were to use cinemode, I would also need to change the shutter speed to what? 1/48 or 1/24?
You have no direct control over shutter speed in cinemode. See the table I linked to above. Have you opened Operator's manual? You can only control shutter speed in shutter priority (Tv) mode; Tv mode and Cinemode cannot be used together.

Whats the best shutter speed to use for more of a film look?
Traditionally 1/48 is used. See the exposure table I linked to, you can see that the camera tries to keep 1/48 as long as possible. It starts ramping up shutter speed after aperture closes to f/8.0 or opens to f/1.8. Between these two points you have 4 and 1/4 f-stops plus additional 2 and 3/4 of f-stop provided by built-in ND filter. This should be enough to keep you at 1/48 shutter unless you shoot bright white wall.

Paul Tarlevs

2008 August 25th, 15:29

What do you mean by "this"? You can control overall exposure in terms of brighter/darker but you cannot control individual settings like shutter speed or aperture. On the other hand you can always check what your current settings are using the Photo button. Then use this table to see where you are at:

http://www.elurauser.com/articles/canon_cinemode_table.jsp

Down the table are values achieved when you click EXP slider to the left, up the table go values when you click EXP slider to the right.

Will your video look like film or not does not depend on this "trick". Using the Photo button is just means to assess your current exposure settings, not to switch the camera into some magic mode.

You have no direct control over shutter speed in cinemode. See the table I linked to above. Have you opened Operator's manual? You can only control shutter speed in shutter priority (Tv) mode; Tv mode and Cinemode cannot be used together.

Traditionally 1/48 is used. See the exposure table I linked to, you can see that the camera tries to keep 1/48 as long as possible. It starts ramping up shutter speed after aperture closes to f/8.0 or opens to f/1.8. Between these two points you have 4 and 1/4 f-stops plus additional 2 and 3/4 of f-stop provided by built-in ND filter. This should be enough to keep you at 1/48 shutter unless you shoot bright white wall.

What I mean by "this" is the gain trick.

Rumpelgeist

2008 August 25th, 15:41

What I mean by "this" is the gain trick.
What do you mean by gain trick?

tiberghv

2008 August 31st, 16:38

i have a mini SD card inside my hv20.
when i half push or push down the photo button, i don't get the aperture and shutter speed to be print on the LCD, instead i get a little flashing signal on the left showing a little red camera and it's writen "off" on it.
the two little buttons on the side of the camecoder are in P mode and tape.

does anyone have any idea off what the problem is ?
thank you

Rumpelgeist

2008 August 31st, 18:14

dig1101

2008 November 1st, 00:00

that really help me a lot without googleing for hours.

Emersk

2008 November 17th, 00:54

In response to Paul Tarlevs' question about whether you can use the EV fiddle trick in Cine Mode, I would say that you can use it to minimize gain and freeze the shutter speed and aperture in low light. The following numbers are for an NTSC model camera. You point the camera at a moderate light source so that the readings on a half press of the picture button are something like F3.4, 1/48. Then raise the exposure steadily until the reading is just changes to 1.8, 1/48 or 1.8, 1/24. Then you know the camera has automatically set the aperture and shutter speed with a minimum of gain. Since the camera is auto adjusting using minimum gain possible and each gain increase is 1.5db compared to 6db for an F stop the camera uses at most 3 gain steps before changing the shutter speed or aperture. At most you will see 3 gain steps before an aperture change which would probably be an acceptable level. This will enable you to avoid the torch gamma settings of TV mode.

It could happen that after freezing the shutter, aperture and gain settings at 1.8, 1/24, 0, the picture is too dark. Then either add light or switch to TV Shutter Priority mode with a shutter speed of 1/12. A shutter speed of 1/12 keeps lips in synch with sound during a talking head interview. A shutter speed of 1/6 enables an HV30 or HF100 camera to see in the dark as well as a person but cannot keep up with lip movement. So when shooting people when it is fairly dark zoomed out at a distance of 3-6 feet where the lip movement is clearly visible you can use a shutter speed of 1/12. At six or greater feet you cannot make out lip movement that well so you can shoot interviews in still darker light at a shutter speed of 1/6 enabling the camera to see what the human eye would be able to see given the low light. Also when shooting people walking or moving slowly the motion blur caused by 1/12 or 1/6 shutter speeds may be less annoying than noise created by gain. A final option is spend an incremental $2,500+ on a camera with twice the sensor diameter and lug around over three times the weight.

My understanding is that you will never get close to the look of film with the HV30 or HF100 (my camera). According to Doug Liman, the director, the Red One will blend in with 35 millimeter footage well. See this Vimeo Interview with Doug Liman (http://www.vimeo.com/1106950) Hopefully the $3,000 Red Scarlet due out in mid 2009 will also mix reasonably well with film.

jerico

2009 January 5th, 09:39

this could be the solution to my grief - does this also apply to the hV30?

sfdex

2009 January 5th, 11:51

I use this trick with my HV30 all the time. Works perfectly.

:D

jerico

2009 January 6th, 19:23

I use this trick with my HV30 all the time. Works perfectly.

:D

With my HV30 - When I'm in movie mode and I press the photo button half down I get the red flashing "camera mode off" icon :hv20-smilie51: I have a memory card in...

what am i doing wrong?

jerico

2009 January 6th, 20:13

Ok - I got it working, but here's the thing: In full Av mode you can traverse the entire aperture gamut (1.8 - 8.0), but whe you use this trick, you can only go as high as maybe 5.6...is there a way to have full selection?

David17

2009 February 13th, 19:10

Great read from Patrick and tutorial!
Thank you.
Is there a way to save this so it can be used after the camera has been turned off and on again? I am guessing not.
David

sfdex

2009 February 13th, 20:34

Unfortunately, as soon as you turn off the HV20/HV30 the settings go away. I've gotten really fast about resetting the controls, though; only takes a moment.

Also, if you are working where you can keep the camera plugged into the AC power supply, the camera won't shut off between takes. It'll spool down and go into a tape-save mode, but it stays on and doesn't lose the settings.

- Dex

navmachine

2009 March 6th, 17:35

I have got to say thanks for the tutorial! I really appreciate all the great info in general in this forum. Now I get to beat the gain game with cheat codes!

navmachine

2009 March 6th, 17:42

With my HV30 - When I'm in movie mode and I press the photo button half down I get the red flashing "camera mode off" icon :hv20-smilie51: I have a memory card in...

what am i doing wrong?

I had that exact same problem. Press the function button and then go to the icon right above the menu icon is the photo menu. You need to turn it to something other than OFF and then you can use the photo button half way. Not sure why its like that, but there you go.

brian911

2009 April 2nd, 21:03

I understand Eugenia's point that underexposing is not fixable in post-processing, while grains can be removed post ... but I rather underexpose than making work for myself in post.

I also understand that some gain is fine. I am happy with a bit of gain to have more details in the scene, but I don't want too much gain.

I've ran several tests using a variety of settings. I've concluded that Tv and Spotlight at the gain threshhold of F1.8 and 1/30 (for 30p at full wide) gives the same exposure. HOWEVER, when I tried with Cine mode at the same settings, the exposure is much higher which leads me to think that some gain is applied. This goes against what I thought - I thought Canon used gain as a last resort? Or does this have something to do with the gamma shift I heard about in Cine mode to give the video a more cinematic effect?

I have the HG21 and I'm admittedly a video noobie.

Slagg Brothers

2009 April 4th, 12:18

Dana Love

2009 April 4th, 13:28

Hi Slagg Brothers,

The best source for information is right here on the board. Check out http://lytecap.blogspot.com/ for details.

If you point the camera at a bright light, you can lock the exposure the camera sets itself to while it's looking at the bright light. So long as the exposure, on full wide, is not 1.8, there's no gain.

Why on full wide? Because as you zoom in, the maximum aperture changes. Just widen out fully, point the camera at a bright light, and lock exposure. Then check and see your results.

If your result is 5.6, the light was too bright. If it was 1.8, the light was not bright enough.

The guy on the board who makes the Lytecap is a genius, in my book. It's a simple way to dial the "right" amount of light in, and not have to set it using random, often uncontrollable lights on scene.

brian911

2009 April 4th, 13:32

I've been lurking in the forum for a while and you all give brilliant and friendly advice :hv20-smilie77: but I have to confess that this exposure lock trick is blowing my brains out.

I apologise for asking the same question but I've been through the newbie threads and searched the others and it quickly becomes overwhelming.

I no longer know whether I have to cap the lens of the HV30 or point it at a light and lock it at f1.8, f2.0, f4.8, or f5.6 . All figures I've seen here or on the Net. When I lens cap, I don't even get a + side to the exposure range, although the writer of the idea has a range into the +ves. I've read and reread the same threads over a few weeks and never seem to nail this, they all seem to spiral into various methods that I rarely seem to replicate.

Has anyone produced the definitive method to lock exposure with no gain?

Apologies for this imposition.
Capping the lens defeats the purpose of trying not to have gain. The article by Barry only capped the lens as a demonstration of what the camera is doing when it doesn't have sufficient light for a decent exposure - it cranks the gain to a maximum 27db.

When you shine a light at the camera (in an otherwise dark location), it fools the camera into thinking there's more light and you either get into an exposure setting outside the gain zone, or you get out of it enough so that you can get out completely by pushing the EV setting in the - direction with your joystick. Remember, each larger EV setting exhausts the following in an order of priority for increasing exposure: 1) decrease F-stop value, 2) decreased shutter speed 3) increases in gain at 1.5db intervals. In other words, gain is a method of last resort for the camera.

In Tv mode, the shutter speed is locked so once the F-stop values are exhausted (i.e. the iris on the lens is fully dilated), the camera starts adding gain. Therefore, in this mode, to check if gain is applied, it's simply finding the threshold where F-stop values stop decreasing, using the photo button. Then you know every + EV setting after that is a 1.5db increase in gain.

But what some people on this board have a gripe about this whole 'trick' is that it usually renders the scene severely underexposed. I think they are right. In one sense, the automatic exposure that the camera selects in dark scenes is too much, but there's 11 steps - EV steps available which can decrease the gain by (11 x 1.5db = 16.5db). Assuming the camera is cranking the gain at a maximum of 27db (very dark room), you can reduce it to 27 - 16.5 = 10.5db of gain without any tricks whatsoever. In most cases, the gain selected by the camera is less than 27db and using the EV steps can get it out of the gain zone without any tricks.

At the end, it's what you want that matters. Here's what I recommend you do in low-light. Use Tv mode and decrease exposure using the EV settings. If you absolutely don't want any gain, or the image is still not sufficiently dark to your liking, THEN use the light trick to force the exposure to be lower.