With today’s complex colour requirements, a shade cannot always be assessed under one light source. Several may be needed so that the shade is viewed in applicable conditions, i.e. ‘Artificial Daylight’ and ‘Point of Sale’ Light.
This allows inconsistencies such as metamerism to be detected. When two coloured materials have identical spectral reflection curves, they will match visually under any illuminant. However, it is possible for two materials to match visually under one illuminant but mis-match under another, such matches are termed ‘metameric’.
How often have we heard the dissatisfied phrase, “The colour looked totally different in the shop!”. Well, that’s metamerism in action. Metamerism is the term used when two materials match visually under one light source but mismatch under a different light source.
This is usually a result of the colouring matter used in each material being different. With these factors influencing colour appearance it is important to standardise viewing conditions, especially for commercial use.