video tutorial on how to control the shutter/aperture/gain

[Patrick Jennings]

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.

[Mal]

BRILLIANT!!!

Great job. I heard all about that, but you explained it really well, and it's very easily duplicated. Many thanks for that.

Any chance we can upoload that video to HV20? Like mentioned here:
http://www.hv20.com/showthread.php?t=36

EDIT: uploaded now: http://hv20.info/yopu/hv20aperturecontrol.mov

Any idea how STRONG or dim the light has to be that the cam has to be pointed to? I'm gettinmg good results from an LCD screen that is showing a light color (light grey, white). It seems a consistent source of light would be advisable to get duplicable results.

And just to add; it looks like the available shutter speeds in Cine Mode for the NTSC version are: 1/48, 1/40, 1/34, 1/30, 1/24, and then 1/20, 1/17, 1/15, 1/12.

I heard about the possibility of a built-in ND filter; any thoughts on that?

[Patrick Jennings]

thanks mal.

i don't mind if you put it on your server. i just don't want to have to upload it again on my super slow internet connection

a consistent light source would be ideal, but it really doesn't matter how bright or dim it is. you just point it at any light, a lamp, a torch, the sun. it's just trial and error until you get the knack of it.

i think it does have a built-in ND. the smallest aperture the lens can do is f/8 but in TV mode you can close it all the way to f/22.... so i think from 8 to 22 there is an ND of some sort.

[David]

The megaupload is down, but I'm looking forward to checking this out.

Thanks!

[Mal]

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


I think worth a watch for ANYONE with a HV20!

[bluegrass]

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]

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, 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]

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.

[Mal]

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! 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".

[24Peter]

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]

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! No, really.

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]

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

[Patrick Jennings]

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

[Mal]

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

You bet!!

[bluegrass]

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]

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]

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]

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]

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]

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]

Patrick,

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

Rick

[Patrick Jennings]

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]

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.

[bluegrass]

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]

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.