Correcting heavily underexposed footage?

[Joe Chao]

In my opinion,it’s very hard.but,have you tried removing the grain in AE with the filter “remove grain”?

[Alexander Gao]

yes, joe. I have tried using the remove grain filter, and it still looks horrible. My picture is VERY grainy, not just a little. The grain affects the picture quality too, it is not just because i don’t like the look.

[Jim Arcon]

My guess is that your camera is a single-chip consumer camera, so you have dark, noisy, and low-color footage. Unfortunately, no amount of post-processing can take your underexposed footage and “…somehow bring my picture out in after effects so it looks properly exposed.”

However, you can probably improve its look. I have had pretty good luck using the shadow/highlights control in AE to improve the exposure (or use Color Finesse if you have it – steep learning curve however.)

The noise filter also makes a significant difference. I usually apply it first, then adjust the exposure. It should get rid of a lot of the noise. It’s a powerful tool and (for me) pretty complicated. It took me quite a bit of experimenting before I really got the hang of it.

For really bad footage, try stacking up two or more layers, then using the screen blending mode. This can improve both the exposure and the color.

Some single-chip imagers in low-light also have a non-random noise pattern. I have heard of a process where you cap the lens, shoot some footage, then “subtract” that noise from the other footage. I have not had any luck there, but the technique is used extensively for astronomical photography (about as low-light as it gets.)

good luck,

Jim

[Renato]

[jim] “Some single-chip imagers in low-light also have a non-random noise pattern. I have heard of a process where you cap the lens, shoot some footage, then “subtract” that noise from the other footage. I have not had any luck there, but the technique is used extensively for astronomical photography (about as low-light as it gets.)”

Hello,

I was very interested in this technique since I also only have a consumer camcorder to use and this could be extremelly handy even if its not perfect…Any way to remove some grain would make me very happy..

So I grabbed my camera, captured some really underexposed footage, as well as some footage with the lens cap on..

I can see the grain on the footage with the lens cap if I mess with the levels, but then I have no idea on how to make it subtract from the underexposed footage…

I tried different blend modes and none of them gave me any improvements, so I was wondering if anyone could point me in the right direction on how this is done, or what kind of tests I can do..

Any ideas are welcome..

cheers

renato

[Ben Rollason]

All of this is subject to the old adage that you can’t put detail back. It’s like trying to unblur an image. You can remove some of the noise, using noise filters, but it will usually simply serve to reveal the lack of underlying resolution in what you shot, making a kind of blurry, blocky mess.

The problem with underexposing and then ‘stretching’ the gain in post is that it pulls out the noise as well as the image. It’s effectively doing the same as the camera does to compensate low light. It’s all about the signal to noise ratio in what you shot and underexposing isn’t going to help that.

The best bet really is to shoot a less grainy image – which means you need more light. I know sometimes that’s simply impossible, but often a little ingenuity can help matters a great deal. Gather together whatever household lighting you can – Maybe change the bulb in the room from a 40 watt to a 100 or 150 watt. If this isn’t an option, you could try making a homemade reflector out of white card or tinfoil to reflect available light back onto your subject. You need to try and light your subject to the point where the camera doesn’t use any gain to expose it correctly. It’s the gain that causes the grain. Gain amplifies the image, but it amplifies the noise too and only more light can improve your signal to noise ratio.

Also, use the white balance feature of the camera – you’ll find it’s much easier to turn your image back to an orangey tungsten look in post (use an orange layer with the color blending mode and adjust the opacity of that layer) than it is to pull any colour out of an image with an orange tungsten cast.

As a post-production tweak, I’d recommend lifting the gamma, using the levels or curves effect. This alters the mid grey point, effectively stretching the shadows a little. It will make your image seem a bit brighter. A gentle colour grade often helps too.

The other alternative is to go with your strengths and use the graininess of what you shot as a feature.

[Trey Selman]

I have and it works well BUT be prepared for a severe render hit.
I did a low light shoot of a violin solo and the 4 minute song resulted in a 45 minute render with the remove grain filter in effect.

But the results were a significant improvement.

[Steve Roberts]

Remove Grain a great effect that samples the existing noise in a clip, then basically creates an algorithm that is the opposite of that noise.

Some “remove grain” tips:

1. You can tweak the areas from which the noise to be removed is sampled by viewing “samples” instead of “preview”. If they’re over the wrong frame in the clip, you can change the sampled frame in the effect controls under “samples” I think. You can also manually place the samples over large broad areas of color if you want.
2. Enable Temporal fltering. (I think that’s what it’s called — I’m not at the AE station.)
3. Feel free to tweak the amount of noise reduction.
4. Take a snapshot with the effect off, then apply the effect and tweak, possibly while viewing the full effect, not “preview”. To see the “before” look, view the snapshot (F5).

It’s a great effect, but if the clip is really noisy, it can end up just looking blurry with the effect applied. That can be a good look, though.

Steve

[Renato]

Thanks Steve for the reply,

I was just really curious to see how to go about setting up the technique that Jim talked about.. Even if it doesnt make a perfect result, I wanted to give it a try to see what kind of results it creates.. If there is anyone else that could tell me how to set it up, I would appreciate it..

But thanks to all for the great advice

renato

[Chad Treanor]

The very fastest way to lighten/brighten video in after effects is to

>bring in the dark video

>duplicate it once

>change the top layer’s transfer mode to SCREEN

and if you need to go brighter then dublicate the screened clip.

this way you can tweak multiple layers (if need be) or edit the first layer with Curves or Levels and then do the duplicate trick. This is super fast and doesnt take as long to render out.

Hope this helps.

later
Chadwik

[Jim Arcon]

Well… like I said “I have heard of a process where you cap the lens, shoot some footage, then subtract that noise from the other footage.” It also occurred to me that at least one photo product (Qimage) has the tool built into the software. Qimage calls it “dark frame.”

Do some searching on astronomical photography – photographing stars and stuff. You would probably use one of the blending modes in AE. A quick poke at Google yielded 1,020,000 hits, the first half-dozen mentioned low-light enhancements.

One technique (https://www.photo.net/learn/dark_noise/) discusses what it terms dark noise. The site calls the technique “calibration” and even gives a recipe for the technique using Photoshop and a low-light still pic.

In any case, all the other caveats apply – amplifying the brightness in any way also amplifies the noise. Removing the noise/grain tends to blur the image a bit. (The temporal control in noise/grain also does same frame to frame averaging that smooths the noise.) But, no matter what you do, it will NOT look as good as if it was shot with more light.

You can (probably) make the images look BETTER using some of the techniques recommended by me and several others in their replies. Some techinques will work better than others on your footage. Don’t be afraid to experiment. But if you have a choice to shoot with more light or a more sensitive camera, it will yield a much better picture than any enhancement you might be able to do.