Metamer Mismatching and Its Consequences for Predicting How Colours are Affected by the Illuminant

Metamer mismatching (the phenomena that two objects matching in color under one illuminant may not match under a different illuminant) potentially has important consequences for color-based machine vision. Logvinenko et al. [1] show that in theory the extent of metamer mismatching can be very significant. This paper examines metamer mismatching in practice by computing empirical metamer mismatch volumes. A set of more than 20 million unique reflectance spectra is assembled using datasets from several sources. For a given color signal (i.e., RGB or CIE XYZ) recorded under a given first illuminant, its empirical metamer mismatch volume for a change to a second illuminant is computed as follows: the reflectances having the same color signal when lit by the first illuminant (i.e., that are metamers) are computationally relit by the second illuminant and the convex hull of the resulting color signals then defines the empirical metamer mismatch volume. The volume of these volumes is shown to vary systematically with Munsell value and chroma. The centroid of the empirical metamer mismatch volume is also tested as a predictor of what a given color signal might become under a specified illuminant.