Color requirements for manufacture and retail are complex and diverse. To ensure product color, several types of light source are used (e.g. Artificial Daylight and TL84, CWF,U35,830. Multiple light sources are also necessary to reveal color inconsistencies and metamerism.
For many products, it is critical to ensure components are assessed under the same illuminants, using defined procedures, in a controlled viewing environment, by everyone in the supply chain. This ensures standardised and repeatable color assessment.
To ensure controlled standardised light, two factors require consideration.
COLOR TEMPERATURE – Kelvin. (K)
Color temperature describes the color appearance of the light and can vary along with its spectral power distribution.
‘Correlated’ color temperature applies to fluorescent lamps and approximates the true color temperature.
Lower color temperatures appear warmer, such as Illuminant A and 830. Lamps with a higher color temperature look cooler or bluer, like D65 and D75.
COLOR RENDERING INDEX (CRI)
A numerical system that measures how well colors are rendered by a lamp in comparison to a reference light source.
CRI is measured on an index from 0 – 100, with 100 being an exact match, low values indicate poor color rendering. D65 has a CRI rating of 98, this shows colors more accurately than a CWR with a CRI rating of 62.
This rating method is recognised by the Illuminating Engineering Society (IES) and the Commission International de L’Eclairage (CIE).
Light sources description:
D65 – International standard Artificial Daylight, color temperature is 6500K. CIR is 98. Specified for most applications where color consistency and quality are required. High conformance to ISO 23603 – CIE S 012/E specifications for accurate colour matching.
D50 – Color Proof “Artificial Daylight” for graphic and photographic applications., color temperature is 5000K. CIR is 98.
D75 – International standard Artificial Daylight, color temperature is 7500K,CIR is 96. High CIE specifications for accurate colour matching.
TL84 – Applicable for stores in China, Japan and Europe, color temperature is 4000K,CIR is 85. CWF – (Cool White Fluorescent) American Standard,color temperature is 4150K, CIR is 62.
TL83 – ( Warm White Fluorescent ), American Standard,color temperature is 3000K, CIR is 85 U35 – One of an American light source , color temperature 3500K. CIR is 85
F – “Sun-setting Light Yellow” incandescent light source (imitation of sunset), Required by BS 950: Part 1 as a test for metamerism (approximating CIE Illuminant ‘A’) color temperature 2700K. CIR is 100
A – Tungsten Halogen Lighting (CIE Illuminant ‘A’). This represents incandescent A (inc-A) with a colour temperature of 2856K. CIR is 100 Typical light source used to check for metamerism.
UV– Ultraviolet Blacklight. Used to detect the presence of Optical Brightening Agents or Fluorescent dyes. Therefore it is useful when assessing white and Fluorescent shades to check the level present and its evenness.