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