HV20 gain

I think the HV20 *only* has automatic gain control and that you can't force it to zero or turn it off. If it thinks it needs gain, it'll put it in there.
 
AuditoryVisuals said:
Too bad. I guess I'll just have to shoot in bright light almost all the time when I get this camera.
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Problem with doing that is, there's no ND filters; it only controls exposure through the shutter speed. So you might find yourself at 1/250 or 1/1000 without realizing it.

I've barely gotten to go through all the features yet, so this is all preliminary.
 
Barry, did you follow those links till the dvinfo.net thread?

That said and probably, you already download and know the manual.

If so on both, what's your guess?
 
My preliminary under-the-gun findings:

I got mine on Wednesday this week, had one day to mess with it before using it on a 3 camera shoot with 2 HVX's (couldn't find another HVX to rent with two hours notice).

For practice, I shot some of my son's school assembly on it; kids in white shirts with strong key lights and black drapes behind them are indeed a good test for exposure issues and gain. My process was interactive, as I was trying to quickly figure out what the HV20 was doing.

Spotlight mode - didn't compensate enough. Bringing down the "exposure" - not enough. Seems to affect shutter speed and aperture with some kind of unholy teamwork. Aperture priority mode - unusable for this situation. Gained up horribly. Again, unholy relationship between aperture and gain.

Cine-mode (the camera mode, same menu as shutter priority, not the frame rate) seemed to keep the camera from gaining up; the other modes would be adding grain I could even see in the LCD when I was on the dark background. I ended up only using the cine mode. I don't know if you can use it with 60i or not. Didn't try it yet. I like the 24F mode in any case, though it's a pain in the butt to remove pulldown with FCP/Cinema Tools.

100% zebra seemed pessimistic (95%?); in any case, transition to overexposure is surprisingly smooth. Very impressed with that. Yes, I know it's clipping at 107 or so, but 100% zebra did seem conservative.

I was really surprised to view the footage HD-SDI out from my Kona LHe. Happily surprised. Low light performance was much better than I expected too.

My 3 camera shoot the next day was three-angle green screen. 2 HVX, 1 HV20. I chose to shoot everything 24, as that is the only mode I had properly tested the HV20 at. I don't like interlacing for green screen anyway. The HV20 cut together quite well with the HVX's. I used it for one of the over-the-shoulder angles, as I find closer shots are more forgiving for lower-end cameras. Manual focus control worked fine with the LCD "enhanced". It's funny using such a small dial to control focus, but it worked. I wouldn't want to have to rack focus on it!

Definitely, test this thing before serious use (as with anything of course, but more so than regular professional gear). But I am very pleasantly surprised with what I can get out of it! Good tool for the toolbox and a great companion to the HVX.

Edit: Shutter speed in Cine-mode SEEMS locked where it should be, 1/48. Another reason to use this mode.
 
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Based on this, I think I've kind of figure it out...(at least how to keep the gain constant)

1) Press the Func button
2) Go into Tv mode (shutter priority)
3) You can adjust the shutter here with the joystick
4) Press the Func button to turn off menu
5) Press the joystick (center)
6) Scroll down until you get to EXP (joystick down)
7) Press up once on the joystick, -/+ will turn white
8) Set EXP to 0 buy moving joystick left/right
9) Press the joystick (center)

- AGC should be off now...I am assuming you guys figure this out too...but wanted to spell out how I did it in case others may be wondering.

Did you guys notice the DOF when in Av setting it to 1.8? Not too bad, buy I just did a few tests sticking out my foot in front of me... LOL will test more on the road this week...
 
Verko said:
Edit: Shutter speed in Cine-mode SEEMS locked where it should be, 1/48. Another reason to use this mode.
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My very early findings when in Cine-mode was that it was too blurry. It definitely did not look like 1/48. More like 1/24. I switched to TV mode and locked it at 1/48 and it looked much more "normal". I am not saying that your footage wasn't recorded at 1/48 but rather you may have somehow locked it there manually or your shooting environment never called for anything but that speed.

Anyone else seeing this?
 
I played with it a bit, and it seems to be really... odd. As in, it's always in auto-exposure mode, and you can choose to lock the shutter or you can choose to lock the aperture.

If you lock the shutter at 1/48, it'll change the aperture (and the gain) and not give you any clue as to what it's doing to you.

If you lock the aperture, it'll change the shutter as much as it wants, and maybe the gain too.

I believe you can lock exposure completely by using the shutter priority mode (to force 1/48) and then pressing the joystick to get the EXP window up and pressing "up" to bring up the exposure override window. That appears to give you some degree of manual control. However, there's no indication as to what you're changing. Are you changing gain? Iris? ISO? No way to know. Is the camera gained up to max, or running at 0dB? No way to know.

I put on the "data code" and recorded and played back, and that lets you see what it chose for shutter and iris, but only after-the-fact. And still no indication of what the gain was.

Then, what's really weird, is that it can handle very dark to very bright conditions without bringing ND filters into play. There are no ND filters in it, near as I can tell, unless there's some sort of odd internal variable ND, which I would seriously doubt. So -- what is it doing? Obviously it's using positive gain in low light situations, but does it have variable negative gain?

Normally the iris is only allowed to range down to f8.0; it's rare to see it go any lower. And at f/8.0 in broad daylight, you'd need something like 1/2000 shutter to get proper exposure. Yet it'll show 1/48th. So what's it doing? My guess is that it's internally adjusting the ISO, which is basically the equivalent of applying a whole lot of negative gain.

So -- what does that mean? What should you use? When's the "zero point" of gain, and how do we find that and use it? One poster on DVInfo suggested covering the lens cap and then bringing up EXP; at that point it should be fixed at maximum gain, and you can turn it down from there -- but how far? Where's zero?

Until I can find out more info, I'm inclined to think of the HV20 as an auto-exposure-only product, and you just can't know what it's doing to your footage. Use Shutter Priority mode, lock the shutter at 1/48, and everything else (aperture and gain and ISO) is ... well, you get what you get, basically.
 
Barry_Green said:
I believe you can lock exposure completely by using the shutter priority mode (to force 1/48) and then pressing the joystick to get the EXP window up and pressing "up" to bring up the exposure override window. That appears to give you some degree of manual control. However, there's no indication as to what you're changing. Are you changing gain? Iris? ISO? No way to know. Is the camera gained up to max, or running at 0dB? No way to know.
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And so what? If it gives you the same result... What for I need to know the backyard? The way is to have a real automatic film crew for free. Without to pay more than what the filmmaker have to pay for the camera. This is what we might call a real indy camera.
 
I guess the real test would be to see some footage in different situations--with the settings recorded, if possible.

There are always the old tricks of putting your hand in front of the lens to lock the iris open, but what makes me nervous is that you don't seem to have any direct control over the gain. I don't know about you, but that's a little scary to me.

Like I said, though, the truth is in the footy. If it looks good under a variety of situations, then we might have a winner in the high-end consumer division.
 
Gordon Prince said:
And so what? If it gives you the same result... What for I need to know the backyard?
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Well, if you're comfortable with the camera deciding that your shot needs 18dB of gain in one circumstance but not another, and not telling you about it, then... well, I guess that's okay for you. But a lot of us would appreciate knowing how the thing works so we can keep a lid on what it's doing, so there are no "surprises" in the editing suite.
 
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