Possible to achieve good basic chroma noise reduction with a preset?

[alpinist]

@rawfiner

@alpinist

a scene that is not illuminated by white but by some other color (R,G,B).

I am not a white balance expert, but the scene is illuminated by a light that has a spectrum: R, G, and B coefficients are not a precise representation of that spectrum.

Seems to be related to brain+eyes: color calibration - Brainblasting... - #16 by anon41087856

@rawfiner

@alpinist

Do you understand why?

The Y0 coefficient (~luma) is computed as R+G+B, with white balance removed (or not depending on the checkbox). The aim is to minimise the noise variance as R, G, and B have (mostly) independent noise.
The formula for U0 and V0 are U0 = R-B and V0 = R-2G+B.
For U0 and V0, the aim is to cancel out the signal, to keep only noise (mostly chroma noise).
When we have a bad white balance before denoise profiled, this cancellation probably does not work well, because R and B can have different magnitude.

Thanks. I tried moving the denoise module after color calibration, but this doesn’t help.