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Topic Rooms Vfx » Conference room » Edge Work » Reddit Discussion on spill suppress and loss of grain color.

Reddit Discussion on spill suppress and loss of grain color.

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Question / Discussionspill suppress and loss of grain color. (nuke) (self.vfx)
submitted 16 hours ago by LA_viking

I'm interested in hearing anyone's solution to replace green grain after a despill operation. After a hue correct or other despill operation, I usually lose most of the saturation and luminance of the green grain. It usually ends up as darker pixels that stand out to me and usually end up as a discrepency between added grain and the despill grain. I can pull back on the despill to get the levels of the grain closer to what they were, but it's a fine line between recovering grain levels and reintroducing spill. As it is now, I try to find a balance.
Does anyone have a nice trick to save a relative amount luminance AND saturation of the green grain without reintroducing too much spill?
13 commentssharepocket

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[–]jedypod 5 points 13 hours ago
One solution would be to denoise your plate, despill after your denoise, then in a separate branch, subtract your denoise from the original plate to get just the grain, then plus that back over your despill result.

[–]axiomatic- 1 point 11 hours ago
Or use add grain (pref from grain roll) at the end across the whole comp - assuming you denoise all the elements.

[–]jedypod 4 points 5 hours ago
In general this approach would not be ideal because you will lose a lot of detail from the original plate.
No degrain is perfect, there is a lot of plate detail that comes along for the ride...

[–]LA_viking[S] 1 point an hour ago
I absolutely agree with this. Early on in my career I degrained and regrained everything. Too much detail gets lost this way.

[–]masky0077 1 point 4 hours ago
this... that is the best way to do this

[–]LA_viking[S] 1 point an hour ago
This solution doesn't fly at my studio. I've been using this technique over the years but it isn't perfect. Supervisors at my studio can pick it out right away and they don't approve.

[–]brass___monkeyCompositor - 10 years experience 3 points 10 hours ago*
Despill on the denoised plate. Divide the result by the denoised plate and then multiply it by the original noises plate. This way you won't denoise the grain.
Like this

[–]LA_viking[S] 1 point an hour ago*
This works beautifully! Thanks!
Will this technique work for paint or would it reintroduce some detail from the original plate and reveal what was painted out?

[–]brass___monkeyCompositor - 10 years experience 1 point an hour ago
I wouldn't recommend doing it for paint work.
If you set the output mask of your paint node to your own channel something like painted.alpha you can regrain only the affected section. But unless you are painting every frame rather than a clean patch I would do it on the degrained plate anyway.

[–]hydrogenjoule 1 point 2 hours ago
Don't you mean subtract and add?

[–]brass___monkeyCompositor - 10 years experience 3 points 2 hours ago
Despilling is a multiplicative process not an additive process.

[–]hydrogenjoule 3 points 2 hours ago
I misread. I thought you were saying divide to get just the grain and then multiply the grain back on. Reading it again, I don't know how I came to that conclusion. Carry on!

[–]hydrogenjoule 1 point 2 hours ago
I think this tutorial on Nukepedia may help you:

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