Often, colours need to be assessed using more than one light source in order to replicate different viewing environments. If only one light source is used for colour assessment, metamerism can easily slip through the net with the potential to cause problems at the consumer interface.
When two or more materials match visually under one illuminant but mismatch under another, the inconsistency is termed metamerism. It is most usually caused by differences in the colouring matter used for each material. To detect metameric matches, you need to assess and match the colour submissions alongside the standards under different light sources.
VeriVide lamps for viewing cabinets covers all supply chain viewing conditions, including Artificial Daylight (D65 or D50), UV, Cool White, Filament and specific requirements of individual major retailers. For colour consistency, the source of light must be controllable and constant and two important factors need to be considered:
- COLOUR TEMPERATURE – expressed in Kelvin. (K)
Colour temperature describes the colour appearance of the lamp itself and the light it emits and can vary along with its spectral power distribution. “Correlated” colour temperature applies to fluorescent lamps and approximates the true colour temperature.
Lamps with lower colour temperatures appear warmer i.e. red/orange and typical examples would be illuminant A and 830. Lamps with a higher colour temperature look bluer, and examples would include the VeriVide D65 and D75.
- COLOUR RENDERING INDEX (CRI)
A numerical system that measures how well colours are rendered by a lamp in comparison to a reference light source. The CRI is measured on an index from 0-100, with 100 representing an exact match, whilst low values indicate poor colour rendering.
Therefore, a lamp rated with a CRI of 98 such as the VeriVide D65 will show colours more accurately than a lamp with a CRI rating of 62 such as the CWF.
This rating method is recognised by the Illuminating Engineering Society (IES) and the Commission International de L’Eclairage (CIE).