Lamp options and paint

Often, colours need to be assessed using more than one light source in order to replicate different viewing environments. The need for different light sources becomes apparent when, for example, consumers complain that a product ‘looked different when we got it home’.

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. 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.

The following table of VeriVide lamps for viewing cabinets covers all supply chain viewing conditions, including the specific requirements of individual major retailers.

Retailers have differing specifications for the lamps and grey used in the Colour Assessment Cabinets. VeriVide equipment provides these conditions for all applications. For consistency, the source of light must be controllable and constant. To understand light sources, two factors need to be considered:

1. 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.

2. 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).
VeriVide servicing

It is important to have your cabinet regularly serviced – a non-serviced lightbox is incompatible with successful accreditation. A cabinet needs servicing when:

• It was bought more than a year ago and has not been serviced in that time.
• The lamps have completed their 2000-hour life cycle. After that time the spectral output of the lamps will change, resulting in assessment inaccuracies.

Without a regular service the build-up of dirt will also discolour both the interior paint and lamps, distorting reflective light and spectral output. This matters because if uncorrected it will make colour decisions unreliable and inconsistent, potentially causing problems in the supply chain.

VeriVide recommend that lamps are replaced every 2000 hours or annually to ensure that their colour matching properties are maintained as these properties reduce with time and use even though the lamps continue to illuminate.