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Old May 9th, 2008, 03:07 PM   #1
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Gain or pain in post?

Hello everyone, here is a technical question that I’m sure all of us has thought about it but never really looked into it.

In low light situation, when you have no control over the lighting and the room is quite dim, you’ve already exhausted every other setting, 24p, slower shutter speed…. Is it better to crank the gain up, in order to get a brighter image , which will generate noise or is it better to keep the gain as low as possible and brighten it up in post. Obviously both will generate noise & artifacts but which one will give you the cleanest image? Does the camera do a better job than the software?

What do you guys think, any personal experience where one was more favorable than the other? Though one huh?
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Old May 9th, 2008, 03:52 PM   #2
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This happened to me on my first shoot. I used the "fix it in post" method (FCP) and I was not happy with the results. I left it as is, and the client was fine with it.

From what I understand, it's better to do all of your adjusting "on the spot". Do as much as you can live
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Old May 9th, 2008, 05:07 PM   #3
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I want the best possible image quality I can achieve under the circumstances in the camera. Fixong it in post has become far too common in the industry today andunfortunatly when that happens it generally isn't going to be any better andmay well be worse. IOW, having the correct WB when shooting is better thantryto fix it in post, using the correct exposure including gain is alwaysbetter thantryingto fix it in post. ETCETCETC.

Now having said that I know that it's not alwayspossible to get the right settings when shooting trust me, been there done that,and I'm not saying that bumping the colors or exposureis a bad thing. WhatI am saying is it's better to get it as right as possible in the camera andsave the fix it in post for enhancing the footage or fixing the stuff when you had no choice but to shoot it the way you were or not at all.

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Old May 9th, 2008, 10:05 PM   #4
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Fixong it in post has become far too common in the industry today andunfortunatly when that happens it generally isn't going to be any better andmay well be worse.
Don, I completely agree with you, but I think Carl's question is not quite the same. He's asking something I've asked myself many times. When shooting in low light, and having exhausted all options that don't create noise, do you gain up in camera to get "proper" exposure, or do you add the gain in post?

Neither is a 'proper' method, both add noise to achieve the same luminance level, but which method is cleaner?

There was a discussion on something similar not too long ago, but I don't think it dealt with gain, though I'm not sure...
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Old May 10th, 2008, 06:30 AM   #5
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Gain up in the camera is what I'm saying. Fix the little stuff in post, enhance the footage in post, get the exposure as right as possible when shooting. That includes gain. Put it in the camera.
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Old May 10th, 2008, 09:49 AM   #6
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Yes Vito that is exactly what I’m saying. And Don I also understand your point of view.

What is hard to judge when you are shooting an event is how dark is your actual footage in low light just by looking at your LCD and how grainy is it when bumped up. Because once you have your Gain up on tape the noise will be there in the final product, there is no turning back at that point. Now if you have a low gain and then in post you can then judge if an increase in brightness is require and have a much finer control on how much noise you are willing to introduce.

Doesn’t that make it more controllable and therefore give you a cleaner image?
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Old May 10th, 2008, 01:54 PM   #7
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For a particular amount of light, the signal to noise ratio is the same either way, gain or no gain. If you brighten a dark image in post, the grain becomes more visible. If you darken a bright image in post, the grain becomes less visible. You're better of shooting the way you want the final product to look.
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Old May 10th, 2008, 02:14 PM   #8
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For a particular amount of light, the signal to noise ratio is the same either way, gain or no gain.
Uh, this is incorrect. Yes, the CCDs (CMOS, tubes, silver oxide) have a certain amount of noise. But this is independent of light. As you add gain, you bring the noise to the 'top' of the picture. You are certainly decreasing the signal to noise ratio--increasing the apparent noise. Put the lens cap on and try it. At 0 gain, you'll see nice clean blacks. At higher levels of gain, you'll see the noise come up.

That's why I got excited when I found my VX-1000 (and cameras since then) have a setting of -3dB gain. This actually REDUCES the sensitivity of the CCDs and reduces the noise.
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Old May 10th, 2008, 09:02 PM   #9
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Gain up in the camera is what I'm saying....Put it in the camera.
Hi Don. Can I ask what makes you believe in camera is better? Have you done tests? Is it common knowledge that I am just blissfully ignorant of?

No offense intended at all. I find this to be an important question, and would love to know the basis for your opinion. I cringe everytime I gain up in camera and see the noise. I almost always use less gain and pray it won't need too much tweaking in post.

Thanks, as always.
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Old May 10th, 2008, 09:19 PM   #10
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I agree that this is an excellent question and one that I've looked for answers to, but have been unsuccessful. I've seen "opinions", but nothing that ever made me feel like the question had really been answered.

As I see it, whether you are upping gain in the camera or upping exposure in post, both are SOFTWARE-driven processes. Gain in the camera is just a feature in the camera's software that causes it to interpolate the image data captured from the CCD differently; in other words upping the gain doesn't somehow make the CCD's in the camera more light sensitive. Upping exposure in an editor also uses software interpolation to change the original data.

So unless someone knows the actual specifics of the software (which will vary from camera to camera AND from editor to editor), then I don't think we'll get a real answer to this.
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Old May 10th, 2008, 09:33 PM   #11
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Travis, the only difference I could imagine between the two processes is that in camera the gain could be applied, then the image compressed to be laid out to tape. Just as changing exposure or shutter speed are operations applied to the image as it comes off the CCDs before (for example) HDV codec compression comes into effect.

In post, we aren't changing the original image, we are changing the already compressed image.

Of course, I am making this up...
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Old May 10th, 2008, 11:04 PM   #12
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Gain is like ISO is to digital cameras. It determines how sensitive the sensors are to light. The higher the gain/ISO the more current passes through the sensor which creates heat and therefore create noise on the image.

But my question still remains, which solution is cleaner, on camera or in post.
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Old May 10th, 2008, 11:54 PM   #13
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I find on camera look better than in the post.
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Old May 10th, 2008, 11:59 PM   #14
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I can add a real shoot Ijust had that answered my question on this.

I had to shoot a theatre presentation on a war. The scene was very dark most of the time. Sometimes just barely a light coming from one side of the performer.

I own a Canon A1 which is NOT good in this kind of shoot due to it's poor low light ability. But at 0db gain it is very clean. So I decided to do the opposite of what I usually do and keep the camera at 0db giving me a clean image to start with in post.
( I usually adjust camera the best I can to allow for an acceptable image in post, or for at least anough image detail to work with in post to save it)
Here was my results...

1. Yes it was very clean, but very very dark. Sometime I could not even see anything on the screen unless I turned all the lights off in the room while viewing the monitor.

2. By the time I brought up gamma, brightness, channel levels, etc to get enough brightness to see the scene it was also so incredably noisy it was discusting looking.

3. I also noticed that the amount of color data that was recorded in the dark room was so low that it almost made it impossible to bring color back into the scene at all in post. That was very hard and sometimes just impossible to do leaving some scenes nothing like the original.

My conclusion....

I should have bumped the gain allowing the chip to capture more color and image detail in the overall scene, and dealt with the noise in post or maybe not at all. The color would have been really nice, the shadow depth and details in the darker areas would have at least been natural, and most of all, the scene would have been as it appeared their which was dark but powerful feeling and looking.

So, gain up to your comfort level, giving the recorded signal enough so you can save it in post.

Hope this helps,

Paul
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Old May 11th, 2008, 12:17 AM   #15
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I guess it's from experience that I prefer to add gain if needed in the camera instead of post. I will add in post if necessary but fell the image is more likely to show artifacing where in the camera it doesn't.
Of course a lot depends on the camera. Sonys, IEVX2000,2100 and PD150/170 and DSR250 all being the same electronics and glass carry the gain extremely well. I've shot at up to +15 with out any real fall out in the image where as my JVC5000 with the Canon 16X well it wasn't so good, but when I threw the Canon 19X on it, it was a whole lot better.
I guess it's the way I was taught, put it in the camera when possible.
As for judging in the LCD I believe that the LCD needs to be adjusted to the room. IOW, try to match the brightness of the LCD as close as possible to the light in the room. Still not a production monitor but at least you have a better look at the image, instead of brightening up the LCD to make it easier to see.

Don
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