Metamerism is the effect where a color that appears the same shade to a second color under certain conditions, e.g., in daylight, may look totally different under different conditions, e.g., when viewed in artificial light such as garage or street lighting.
Apart from the individual nature and the many variations of human color perception, there are various other reasons for the occurrence of metamerism.
- The pigment and/or base color composition of the repair paint does not correspond to the pigment composition of the original paint
- The mixing of an unknown color shade (where no mixing formula is available) without checking the shade under different light sources before use
- Tinting of a color without reference to the base colors used in the color formulation, i.e. tinting with a base color which is not part of the original color formulation
HOW TO AVOID
For unknown color shades, metamerism can only be avoided with the use of colorimetric devices. For known shades (where the mixing formula is available), the shade must be checked under different light sources. Tint only with mixing bases which are part of the mixing formula and/or as specified on the color adjustment chart.
Slight variations in color due to metamerism can be overcome by blending into the surrounding areas. For severe metamerism, the color shade must be re-mixed or reassessed by electronic color measurement.