Comparisons between color‐space scales, uniform‐color‐scale atlases, and color‐difference formulae

Abstract Color‐space metrics are considered and three main aspects are analyzed: (1) the distinction between small and large color differences; (2) the relation between space metrics and color‐difference formulae; (3) the color‐scale comparison between CIE 1931 and CIE 1964 observers.The analysis, based on daylight adaptation, is made for the 2° visual field on a chromaticity diagram with uniform scales according with the MacAdam ellipses 1 and, for the 10° visual field, on the OSA‐UCS. 2,3 The conclusions are: (i) the main difference between 2° and 10° observers is a proper dilation of the chromaticity scales; (ii) the chroma scale of the Munsell system is uniform for the 10° visual field; (iii) the scales of the Munsell system are in good agreement with those of OSA‐UCS; (iv) the usual color‐difference formulae (CMC, CIE94) represented on the OSA‐UCS space show a distortion that seems due to their definition in the CIELAB space; the BFD formula shows a lower distortion. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 351–361, 2001