A methodology has been developed to digitize images from photographic color paper (reflection prints) and store the spectral information as a function of the three dye density basis functions inherent to the paper film type. The result is a highly accurate digitization of the spectral information at each spatial pixel that can be digitally stored with very little additional storage space over conventional RGB-type methodologies.
Bruce Glasgow, Thomas McElwain, Lon Pringle, "Spectral Digitization of Color Photographic Paper Through Dye Density Estimation" in Proc. IS&T 3rd Color and Imaging Conf., 1995, pp 148 - 151, https://doi.org/10.2352/CIC.1995.3.1.art00039