SR EN 13523-3:2021

This document specifies procedures for determining the instrumental colour difference (CIELAB) of an organic coating on a metallic substrate compared to another one used as a reference (usually called reference) and the metamerism depending on the illuminant. When two colour specimens have identical spectral reflectance curves, they are matching under any illuminant irrespective of its spectral characteristics. This is termed a “spectral match”. It is also possible for two colour specimens having different spectral reflectance curves to match visually under a given light source but not to match under another light source with different spectral characteristics; such matches are termed “metameric”. One quantitative description of metamerism is the so-called “metamerism index”. Information on the metamerism index is of limited value where ?E (instrumental colour difference for a given illuminant) is > 0,5. The metamerism index is not suited for determining the absolute colour difference or colour consistency of a given specimen at change of illuminant. The colour difference unde