denoise before levels, or levels before denoise?

[swiego]

I have some dark, noisy clips I'm trying to work with. Near as I can tell, in both cases there is a noise-vs-detail balance that I have to control with the denoiser, as would be the case with any other video, but I'm wondering whether it makes a difference whether I adjust levels (gamma, saturation, brightness, contrast, HSV, etc.) first then kick off the denoiser, or vice-versa. Any opinions, or does it not matter? (I'm leaning toward the "it does not matter" school of thought after some experimentation.)

[jagabo]

Levels first, denoise later. You'll get less posterization banding. Take for example a video where all the levels run from 16 to 32 (plus noise). After denoising then stretching to 16-235 you'll only have 16 different intensities. If you change the levels first you'll have much smoother gradations after denoising. In this example you'll you'll need to use much stronger denoising if you change levels first.

Of course, you could use a filter like gradfun2db() to reduce the banding in the first case. But avoiding the banding in the first place will work better.

[sanlyn]

I've often thought I got cleaner and often easier denoising if fixed bad levels first. Thanks for clarifying that issue. However, detailed color correction is another matter; denoising will often affect many color details, especially if the noise has a strong color component like bad rainbows or border stains. It depends on the specific project. I had one VHS transfer project with such badly faded and stained color, that fixing levels and overall color balance were necessary before any other work could proceed. Getting down to fussy color tweaking came after the color-balance/staining + levels + noise repairs.