ISO 18314-4:2024
Analytical colorimetry — Part 4: Metamerism index for pairs of samples for change of illuminant

Scope: This document specifies a formalism for the calculation of the illuminant metamerism of solid surface colours. It cannot be applied to colours of effect coatings without metrical adaptation. This document only covers the phenomenon of metamerism for change of illuminant, which has the greatest meaning in practical application. In the case where chromaticity coordinates of a pair of samples under reference conditions do not exactly match, this document gives guidance on which correction measures to take. Regarding the reproduction of colours, the metamerism index is used as a measure of quality in order to specify tolerances for colour differences between a colour sample and a colour match under different illumination conditions. The quantification of the illuminant metamerism of pairs of samples is formally performed by a colour difference assessment, for which tolerances that are common for the evaluation of residual colour differences can be used. NOTE In the colorimetric literature and textbooks, the term geometric metamerism is sometimes used for the case where two colours appear to be the same under a specific geometry for visual assessment and selected standard observer and standard illuminant pair, but are perceived as two different colours at changed observation geometry. The term geometric metamerism is different to metamerism described in this document.

ISO 18314-4:2024 Referenced Document

CIE 015 Colorimetry, 4th edition
ISO/CIE 11664-1 Colorimétrie — Partie 1: Observateurs CIE de référence pour la colorimétrie
ISO/CIE 11664-2 Colorimetry — Part 2: CIE Standard Illuminants
ISO/CIE 11664-4 Colorimétrie — Partie 4: Espace chromatique L*a*b* CIE 1976

2024 ISO 18314-4:2024 Analytical colorimetry — Part 4: Metamerism index for pairs of samples for change of illuminant
2023 ISO 18314-4:2023 Analytical colorimetry — Part 4: Metamerism index for pairs of samples for change of illuminant
2020 ISO 18314-4:2020 Analytical colorimetry — Part 4: Metamerism index for pairs of samples for change of illuminant