Profiled denoise: separate denoise methods for Chrominance and Luminance
Recently, as I've had a client shoot with rather bad lighting conditions, I was experimenting how to produce denoising results with darktable that come close to the denoising of RawTherapee. I found that it is not easy to do so, as RawTherapee manages get very clean results regardin color noise and also reduces luma noise quite well, as it preserves more detail than DT's Profiled denoise with wavelets, but still does not produce blotchy artifacts like the NL means.
However, there seems to be a way to come relatively close to RT's result at least, by using two Profiled Denoise modules:
The one on the top uses wavelets with the blending mode set to Color, and the module below uses NL Means with Blending mode set to HSV Brightness.
However, using this approach, the Luma-Denoised data from the module below is fed into the chrominance denoise using wavelets. I believe that it would be useful to control chroma and luma denoise independently in the profiled denoise module.
It would provide the benefit of simpler and more straight foreward control for the user and also chroma and luma could be denoised paralelly in one step, without using the already luma-denoised data for chroma denoising.