Depending on the bits ... the total chroma/luma data in the file ... you can only go so far before banding/artifacting come to join the party. And you're doing some pretty heavy changes there. That would take a very properly exposed 10-bit file, if not 12-bit, to work well.
And if this is 8-bit, well ... you can't get there from "here".
So ... what is that media, what shot it? Your original is pretty low in contrast, and you're upping it a LOT ... maybe lighting for higher contrast and adding some gels in shooting will get you a good share of the way "there" and you won't have to grade so hard.
Hey Neil - ! Thanks for chiming in. It's 4:2:0. I suspect under-exposed gradients are where 8-bit really screws you. In my particular case, the BG imagery is so simple that I'd think there's some plug-in that could do it. I remember using "smooth screen" as a technique for this in the past.
Forgot to mention - the background color is definitely power windowed which doesn't help me either !
Here's what I've tried:
- Neat Video Reduce Noise V5 (not great on debanding after removing other noise, which it is great at)
- RG Denoiser III (did nothing for me for this type of thing)
- Flicker Free (this is not what this product is for, but it's fixed other things for me magically before so gave it a shot in the off chance the banding is consistent enough to be analogous to refresh bands)
- Boris FX Deband (I can see how this could be massively useful but wasn't quite right to solve this issue)
What actually worked best? Instead of using Lumetri:
I used Colorista's Key Mode to cutout the BG as cleanly as possible, knowing not to push the limit too much.
Then I threw a Magic Bullet looks set up on top of it (because I've built out my Lumetri setup clone in MB looks to A/B things in the past) and.... the banding is almost completely unoticeable. Crazy.
MB Looks shows all kinds of gnarly banding in its preview window (a gripe I have with RG's previewer not being WSIWYG):
Whaaaaa??? Still there but so smooth now. Mission accomplished it seems (though I'd prefer to use Lumetri).
Then, just for fun, I turn Neat Video On and render the frame and I end up with this:
Hmmm it's almost as if there's something happening within the Premiere engine that interprets noise and compression differently... The footage is HEVC H265 whcih I know has a whole host of problems with Adobe. This one is really specific!
For those encountering a similar banding issue, the solve might be "as simple as rethinking your FX stack." 🤣