Multiple metamers: Preserving color matches under diverse illuminants

Abstract

AbstractThis article extends matrix‐R operations, developed by Cohen and Kappauf in 1982 and 1985 and by Cohen in 1988, to create generalized metameric object color stimuli, here termed multiple metamers, that remain metameric with respect to several different illuminants. As discussed in prior literature, matrix‐R operations resolve any radiometric function (specifying a color stimulus) into a fundamental color stimulus and a residual or metameric black, as hypothesized by Gunter Wyszecki in 1953. The fundamental is sensed by the visual system while the residual is ignored. Metameric color stimuli comprise the same fundamental but different residuals. Thus, matrix‐R operations easily construct metameric suites under an equal‐energy source or under any other illuminant whose physical specification is incorporated into the radiometric function of the color stimulus entering the visual system. In the present article, matrix‐R operations are extended to create metameric stimuli that theoretically remain metameric with respect to an arbitrary number of sequential illuminants. While the stimuli remain metamers under different illuminants, the color sensation evoked with respect to one illuminant is generally different from the color sensation evoked with respect to another illuminant. Examples demonstrate multiple metamers with respect to CIE standard illuminants A and C and with respect to four artificial illuminants. In principle, extended matrix‐R operations create multiple metamers with respect to different observers, or with respect to any combination of observers and illuminants.