The adjustable parameters in a MacAdam-modified version of Friele’s 1965 proposal for calculating color differences have been optimized, according to a criterion of MacAdam, to fit PGN experimental data. The mean-square error of fitting is 0.030. The distribution of the resulting color-metric coefficients more closely approximates those of the PGN data than do previous versions of Friele’s proposals. The optimized primaries have chromaticity coordinates of x = 0.74054, y = 0.25946 for the red; x = −1.11696, y = 2.11696 for the green; and x = 0.13939, y = −0.03454 for the blue primary.
© 1967 Optical Society of America
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