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.
Originally Posted by guru
Originally Posted by bluegrass
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.
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.
Originally Posted by bluegrass
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)
Last edited by crobs808; 2007 May 31st at 16:03.
2007 June 12th, 20:07
Photography basics and the HV20
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!
2007 June 12th, 20:46
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. :-)
2007 June 14th, 12:41
Can you post a written description of the video?
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
2007 June 15th, 08:46
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.
UPDATE: I bought an SD mini card so I could check aperture in the method suggested, however it appears the pal version does not let you half press the photo button in video cartridge mode to check aperture, it blinks the mini card icon at me and then if I change to SD mode I've lost the exposure lock in cartridge mode when I switch back.
Last edited by VaNdaL; 2007 June 20th at 07:15.
2007 June 20th, 01:19
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.)
Originally Posted by VaNdaL
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.
Last edited by CJDaniels; 2007 June 20th at 01:29.
2007 June 20th, 07:09
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.
2007 June 21st, 16:44
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
Originally Posted by VaNdaL
2007 June 23rd, 00:29
I got it now, need to go to still rec in menu (tape mode).
Originally Posted by CJDaniels
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?
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
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
Last edited by Patrick Jennings; 2007 June 23rd at 18:14.
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!
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.
2007 June 24th, 20:10
Ah. So you cannot get f/1.8 fully zoomed in. It won't let you?
Originally Posted by Patrick Jennings
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
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?
Excellent job, Patrick!
Here's a TEXT link I found right here on HV20.com, but points to DVXUser's HV20 forum.
Open the "full article" link and enjoy...
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
Last edited by Worley; 2007 July 3rd at 11:51.
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?
2007 July 16th, 21:53
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?
2007 July 17th, 00:47
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.
Originally Posted by HCoremark
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.