I’m using ART for developing RAW photos and I have included a white balance card in my photos. I’d like to measure the white balance from the card and apply that white balance in ART.
I am using command line processing so I have set up a script to edit the .arp profile and set the White Balance / Setting to CustomMult and to set the values in Multipliers. I know where the white balance card is in the photo, so I am using Python rawpy (which uses libraw) to read the average raw camera red, green and blue values from the white balance card. I am reading these values before any colour transformation or demosaicing is applied by libraw.
My problem is that when I set the ART Multipliers using the values from libraw, the output image (viewed in ART or via TIFF 16-bit export) has a very strong colour cast. I have checked the verbose output of ART and I can see that my Multiplier values are being picked up in the “preprocessing” step.
The Multiplier values that I am measuring also do not match the values I get when I use the Customer Multiplier Pick tool in the ART GUI.
In what colour space are the CustomMult Multipliers defined? In which part of the pipeline are they applied?
Thanks to the ART devs for a great tool (and to the RT devs as well)!