reducing grain/video noise in video cinestyle

J

JohnP

Member
I have a question about reducing video noise. I know when shooting film you can overexpose 2/3 of a stop and then have it printed down in the telecine to reduce the film grain and up contrast slightly. Will this same approach work in video, e.g. overexposing 1/2-1 full stop and then bringing it down in post? Obviously you must be careful not to clip the highlights. But otherwise could this be an effective way to reduce video noise?
 
I was under the impression that most information in DV is stored in the darker areas, and thus underexposing was a good idea.

I've been underexposing about half a stop on all my shots.
 
I'm trying to find some noise-reducing techniques too. I've heard proper exposure and lowering the detail level makes it less noticeable. I've also heard that your suggestion works. I'll have to let you know after the stuff I shot yesterday is finished. It was noisy as hell and no matter what I did in-camera I couldn't get rid of it. As for what John said, I think that's more of an overall rule with video because it's easier to raise the video level while preserving detail rather than lowering it. Once a white is clipped you'll never see any detail in it no matter how much you lower it. Blacks apparently are a little different (not really sure exactly why, perhaps its hard to crush them while shooting?). Hope that helps and if anyone can elaborate, please feel free.:thumbsup:
-Ryan
 
In digital photography most of the information is stored in the highlights thats why you are supposed ot expose for the shadows particularly when shooting digital rather than film. I know that if you are shooting in very contrasty light on film it is better to overexpose and underdevelop this reduced contrast and actaully improves grain size to be smaller. I dont think there is a way to do it in digital becasue the "developing of it sorta goes hand in hand with first capturing it. noise is defnitly more noticable in darker areas however.
 
Thanks guys for your input... but, so far you seem to be offering contradictory info. Barry, please enlighten us!
 
John,

DV is unforgiving in how it clips highlights. You need to expose in such a way that you are not clipping highlights, that is for sure (unless you are intentionally clipping highlights).

In film there is a lot of wiggle room in over- and under-exposing, then push or pull processing. Video doesn't give you all of those options. However, I will note that I did a project where I was attempting to emulate the film cinematography of Gordon Willis on The Godfather, where he intentionally underexposed the footage a full 1.5 stops, and push processed to restore 1 stop back, to get a gritty and different look. I underexposed my video and "push processed" via a gamma correction in post. I got the look I was going for, it was quite nice.

Anyway, underexposure is safe. Overexposure is a no-no.

Other than that, I think it comes down to the basic principles of shooting good video: expose properly, white balance accurately, if you can work your exposure and zoom into the sweet spot for the lens system (usually somewhere in F4-F8 and medium zoom), light your scene, keep you lighting ratio in a managable range for the camera, get to know the settings and balance them to get the detail you want while avoiding excessive noise.

Josh
 
I agree with many things that Josh says but I disagree with overexposure being a no no. Obviously you don't want to clip your whites but I find a dark shot brought up in post creates more noise and milky blacks...a slightly overexposed scene brought back down may not nessiarily bring you less noise but it would definitly not add any. Just remember this is video, we work in a very little latitude, much more than a stop or two off and your WAY off so when you under or over expose do so in moderation and also watch your whites!
 
I think I remember reading that on most DV cameras your latitude is spread something like 4 below and 2 above key, if you have 7 stops of latitude.
 
Thanks all for your posts.

I want to say quickly. I do of course realize that with DV you are working with less latitude, poor highlight roll-off and less highlight compression than with film. Clipped highlights are the hallmark of bad video, but assuming you are careful to watch your highlights, it seems like a small over exposure e.g. 1/2 stop could yield better noise in the blacks, and mids. For example: I finished a short with the dvx-100a and came out with generally clean blacks, however in the lower midtones especially the reds there was considerable noise. Perhaps this is just a limitation of the camera, but if it can be reduced then great.

I'll be shooting a music video with it in the coming month and I plan to do some tests. I will test this particular noise issue and post the results if anyone is interested.

Thanks,

JP
 
Hey guys,
i have to jump in on this one. One of the things I've been most dissapointed with in my dvx was the noise issue. I have gone both ways of trying to slightly overexpose (but often avoided if I can) and underexpose to rid of some of that nasty noise. I'm pretty new to this field so I've pretty much assumed that it was the user error. JOhn P if you find anything leading us towards less noise please post the results. Much appreciated.

D
 
Agreed.

But even in reasonably well lit footage the DVX has seemed to exhibit excess noise. I'll post a video clip in a couple days when I get back to my editing machine. (out of town right now)
 
DPwannaB said:
I agree with many things that Josh says but I disagree with overexposure being a no no. Obviously you don't want to clip your whites but I find a dark shot brought up in post creates more noise and milky blacks...a slightly overexposed scene brought back down may not nessiarily bring you less noise but it would definitly not add any. Just remember this is video, we work in a very little latitude, much more than a stop or two off and your WAY off so when you under or over expose do so in moderation and also watch your whites!
Click to expand...
Hey, no problem. When I said overexposed, I meant clipping whites, but I wasn't clear about that. Yeh, you don't want to clip whites (unless that is your intent). If you can safely overexpose without clipping whites, sure, go for it. However, I havent' been in many situations where I could do so.
 
I have had limited succes finding the channel with the most noise on it (usually blue) and using a slight channel blur on the clip.

I have also played with using 3-4 copies of the clip with increasing amounts of AE's Median or Dust and Scratches filter, with the layers having the most of the effect at low opacities and as the clips get less of the effect, higher opacities.

The results have been very impressive for some shots, and not impressive at all on others. There are possibilites I think, I just have to lock down the combos.

That and shooting with good light.
 
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