A Spectral Estimation Theory for Color Appearance Matching
There are several reports describing color vision in subjects who are dichromatic in one eye and trichromatic in the other. Formulae fit to the between eye color appearance matches in such unilateral dichromats have been used to predict color appearance for dichromats [1][2] In this paper, we describe a general principle, spectral estimation theory, that guides how to predict the mapping from two cone class absorptions in a dichromatic eye to three cone class absorptions in a trichromatic eye. The theory predicts matches by first estimating the smoothest, non negative, spectral power distribution that is consistent with the measured cone absorption rates (e.g. of a dichromat) We then use this spectral estimate to calculate the absorption rate for the missing cone type (the standard color observer) In addition to predicting color appearance of dichromats, the theory predicts color appearance matches between color anomalous subjects and the standard color observer. Finally, the theory offers guidance about the possible effects on color appearance of gene therapy treatment for colorblindness. Introduction Many students of color vision have asked how the color experienced by one person may appear to another person. A fascinating series of papers describe one attempt to answer this question by measuring between eye color matches measured in unilateral dichromats: these people are dichromatic in one eye and trichromatic in the other. The between eye color matching experiments were first reported by Judd et al. [3] and subsequently by Graham et al. [4] and Alpern et al. [5] Judd et al. [3] reported that equal energy light and two narrow band lights at 475 nm and 575 nm look the same when presented to both eyes of a unilateral protanope and a unilateral deuteranope. Alpern et al. [5] conducted a similar experiment with a unilateral tritanope and reported three eigen colors: equal energy light, narrow band light at 485 and 660. [5] reported We refer to lights whose color appearance match between the two eyes of a unilateral dichromat as eigen colors. In 1995, Vienot et al. [1] used the data from these unilateral dichromats to calculate the equivalent color appearance in a standard color observer. Vienot et al. [1] and later Brettel et al. [2] noted that eigen colors define an empirical map between two cone coordinates in a dichromatic eye and three cone coordinates in the trichromatic eye. They fit a piecewise linear relationship from the measured to missing cone types using the eigen colors.
Color Imaging: Displaying, Processing, Hardcopy, and Applications