Calculation of metameric reflectances

Object‐color metamerism becomes visually apparent if two objects match under one light, but not under a second. In the present article, a method is derived by which metameric object colors can be calculated, given the light under which they are to match, and the light under which they are to mismatch. The method gives practical guidance for avoiding or achieving metamerism. The method is not primarily a matter of trial and error and statistics, but depends on a simple calculation that operates on the spectral power distributions of the two lights, along with a set of three color matching functions. The method can deal as well with “observer metamerism,” meaning the effects of observer differences.