In-camera gain versus brightening in an editor at DVinfo.net

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Old October 26th, 2010, 02:29 PM   #1
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In-camera gain versus brightening in an editor

There are times when shooting in a dark location that a decision needs to be made regarding the use of gain in the camera to brighten the footage. Of course, the trade off when gain is used is video noise. That's not good but neither is dark muddy video so it becomes a choice of the lesser of two evils.

One of the choices is to leave the gain alone with the intention of brightening the footage in post. That works to an extent however, if the footage is so dark that detail is buried in the mud, there is nothing there to brighten.

In less severe cases, brightening in post is a reasonable option. However, brightening in post also adds noise. I'm curious if anyone had done any testing to determine which adds more noise - increasing gain in the camera or brightening the video in post.
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Old October 26th, 2010, 09:09 PM   #2
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I would imagine the results would be entirely dependent on the camera and NLE used... So there's a variable or two here.
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Old October 27th, 2010, 12:00 AM   #3
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I've tested this with an hv-30 and gh1. I don't have anything to back up what I say but in both cases when performing this experiment I found that using gain was a better alternative than not using gain. These where incredibly dark situations and with gain on max for both cameras I could barely see an image. Boosting the non gain images for both cameras in post turned out terrible and I couldn't bring back some information. When using gain yes the image was noisy but at least I could make things out.
It depends on the situation, but when you don't have a second chance and its way to dark to get anything normally(reality TV) use gain....you can't bring back information that's not there but you can run neat video.
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Old October 27th, 2010, 12:11 AM   #4
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Personally, I find that using gain and Neat Video gives me the better image. Whenever I've tried to brighten low light footage it almost always seems to end in unusable or very disappointing footage.
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Old October 27th, 2010, 12:57 AM   #5
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If you absolutely need to capture something, you should really just crank up the gain as needed. Increasing the gain is really increasing the sensitivity of your camera's sensor. The byproduct of that extra sensitivity is noise, but at least you'll be capturing whatever it is that needs to be captured.

When your camera's sensor captures an image, that particular frame undergoes a significant amount of processing by the time it gets written to tape or a memory card. During that process, much of the color information is thrown away. Also, if you're using a Long-GOP kind of format like H.264 or HDV/MPEG2, the camera is tossing out even more data. Even the best NLE title can't enhance what isn't there- and this is why brighten/contrast and color correction controls are best suited to tweaking video that's already been properly shot.
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Old October 27th, 2010, 10:01 AM   #6
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Always crank up the gain. You can probably get away with +9dB. There is a balance you have to battle: too little light and you get video imaging noise; too much gain and you get amplifier noise. Go for the gain noise. The earlier poster's suggestion to de-noise is an EXCELLENT one. De-noising software really and truly works. When you first try it you will be amazed. Be warned, though... the compute time to transcode timelines with de-noising effects is HUMUNGOUS!!!

I've used Neat Video denoise software with excellent results. Reg Giant has something, too. There is also Topaz. All of them have demo versions so you can try them first. Neat Video denoise only costs a hundred bucks. I think that the others cost about the same.

De-noising software will routinely turn unusable footage into usable footage. You will stand in awe when you see it.
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Old October 27th, 2010, 12:45 PM   #7
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I completely agree. I do exactly that; that is I set the gain as needed to get the correct exposure and 'fix' any gain noise as necessary with Neat Video. I just wanted to hear other opinions because I occasionally run into someone who believes the use of gain is a mortal sin or something. They always speak to it with a 'spin' that implies they are somehow superior because they don't use gain.
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Old October 27th, 2010, 02:05 PM   #8
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Well, it all depends on the kind of work you do. If you're shooting a film or commercial project and going by professional standards, you had better not use that gain- because you should be using lights on your set. For ENG or run-n-gun kinds of projects, or for really low end documentary work or other situations where bringing lights in or moving to a different location is out of the question, turning up the gain is really the only option.

One of the unfortunate aspects to this industry- and many others- is that you'll run into purists and fanatics, people with really strong opinions and those that are really set in their ways. Some of these people can offer great advice underneath the sarcastic remarks and negative comments, but you have to learn to weed out the trash talk and look at what works best for you (and your client) in a given situation. Also, we're all on different levels of the professional ladder, and sometimes some of us forget that. If you're working on a $6,000 TV commercial, you'll be using extra lights and not cranking the gain. But, if you're shooting a $500 wedding reception in an old, dark Moose Lodge and have no budget for lights, well, that gain knob isn't looking too bad anymore.
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Old October 28th, 2010, 01:02 AM   #9
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Turning up gain or brightening in post is essentially the same thing - "amplifying" both signal and noise. The benefit to turning up gain in camera is that the camera is "amplifying" with far more precision. Once you've recorded a dim image at 8 bits of precision, if it's really, really dim, you just don't have much dynamic range at all to work with ("round off error" from analog to digital conversion is "amplified" just as much as the original signal and noise, when you brighten in post).

How much gain "you can get away with" depends on the camera. Some are far cleaner than others. The HMC40 really impressed me when I first saw how clean an image it can produce at 12dB gain.
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Old October 28th, 2010, 01:07 AM   #10
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An excellent denoiser is MSU's denoising filter for VirtualDub ...and the price is right - free.
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