Intersections of the Spectral Reflectance Curves of Metameric Object Colors

Two reflecting surfaces which are metameric under a particular illuminant must have spectral reflectance curves that intersect. The possibility of metamerism depends on the number and the spectral positions of the intersections and on the shape of the particular spectrum locus in the chromaticity diagram which applies to a given color space. The relevant rules are derived for ordinary trichromatic vision, and the extensions necessary when metamerism rests on more than three matching conditions (e.g., metamerism for both photopic and scotopic vision) are discussed.