Dimensions of factor spaces of spectra of color prints in various spectral representations have been investigated using principal component reconstruction and cross validation of color differences between original and reconstructed spectra. Extensive sets of spectra of color prints printed by various graphic arts technologies have been studied. It has been shown that the most reliable reconstruction is achieved using space of logarithms of reflectance factors and empirical ψ–space. The dimensions of primary factor space of these spectral representations depends on actual printing technology and vary from four for CMY and CMYK prints to six for Hexachrome® and spot colors prints.
Michal Ceppan, Jozef Fedák, Vladimír Dvonka, Michal Veselý, Oldrich Zmeškal, "Factor Spaces of Spectra Sets of Color Prints" in Journal of Imaging Science and Technology, 2003, pp 171 - 184, https://doi.org/10.2352/J.ImagingSci.Technol.2003.47.2.art00012