This question is addressed to those keen on Lab color processing in Darktable.
There are methods to adjust L-channel with various ways of taking references.
Say I have a RAW image with an adjusted L-channel. Simply picked light areas for lights and shades for darks reference -and voila - I have an S-curve in L-channel.
Unlike L-channel, with only gray color, a- and b-channel have two colors each. They make up a more complicated set to adjust. Also, human eye views chroma differently than lightness.
I did not find any good advice on Internet except there is Margulis, but I don’t need that deep knowledge.
I’d like to learn in general terms what shall be taken for reference when adjusting chroma with fewer deviations.
Question: How would you adjust a- and b- channels in DT? What sign-posts would you take for reference in chroma?