There are standard "colour targets" available from photo suppliers. The one I am using is called a Q70 card (I think) and is from Kodak. We have been using the Pixel!FX scanner software (by Mentalix), and it provides a calibration routine against that colour target.
It might be a good idea to build a similar calibration routine into the SANE frontends. Scanner lamps do age, and the standard calibration against a black+white portion of the scanner casing does not get rid of discolorations. Regards, Ulrich Deiters
