Color Errors, Metamerism and Color Ellipses

This paper is about calculation of index of metamerism for the change of observer and comparisons with various color errors and tolerances. — There are two major aspects for color measure in visual reproduction. One goal is to measure the performance of reproduction equipment. The other aspect is related to the audience visual perception. On the one hand human perception is characterized by its variability and, on the other hand, technological trends in reproduction are adding new color source characteristics. — Metamerism is ensuring the viability of trichromatic reproduction. In fact, traditionally, any reproduced color is rendered with a mix of three primaries. It is giving a perception similar to that of surfaces in front of the camera which have various complex spectra so long as those spectral surfaces lie within the trichromatic gamut of the selected reproduction primaries. — Various metamerism indexes have been defined to give a measure of the differences in color matching. The metameric index for change of observer may be used to directly evaluate human perception variability found in any audience for a given reproduction system. At least this can be computed for a set of representative colors. — But new reproduction systems are based on primaries spectra differing sensibly from the ones previously used with Xenon light source. The method for calculation of the index of metamerism for change of observer is using the Standard Deviate Observer data in addition to the Standard Observer data. — The magnitude of color errors induced by this phenomenon is compared with JND found in MacAdam study. It is also compared with existing tolerances in color accuracy. — In fact, the tolerance expressed in current standards are much larger than the variations caused by the observer variability.

Published

2019-10

Content type

Original Research

Keywords

Metamerism, Metameric index, Color difference, Color ellipse, MacAdam ellipses, Color error, Color space, Uniform color space, Color gamut

DOI

10.5594/M001878