Co mparing the colour appearance under different light sources
The effect of colour rendering
The colour rendering of a light source is an indicator for its ability of realistically reproduce the colour of an object.
Following the CIE (Interna tional Lighting Commission), colour rendering is given as an index between 0 and 100, where lower values indicate poor colour rendering and higher ones good colour rendering. The colour rendering of a light source is compared to daylight if its CCT is >5000K and to a black body (i.e. a source that produces a contin uous spectrum) otherwise.
|
Co mparing the colour appearance under different light sources |
The effect of colour rendering |
The make a comparison of the colour rendering qualities of light sources easier, colour rendering group s have been introduced:
| Group | Ra | Importance | Typical application |
|---|---|---|---|
| 1A | 90...100 | accurate colour mat ching | Galleries, medical examinations, colour mixing |
| 1B | 80...90 | accurate colour jud gement | Home, hotels, offic es, schools |
| 2 | 60...80 | moderate colour ren dering | Industry, offices, schools |
| 3 | 40...60 | accurate colour ren
dering is of little importance | Indust ry, sports halls |
| 4 | 20...40 | accurate colour ren
dering is of no importance | Traffi c lighting |
The CIE colour render ing groups
Some tasks such as colour matching in the printing industry have high demands in accurate colour renderi ng and require special attention from the lighting designer. For normal offices, however, the colour rendering group will be 1B or 2, which is easily achived with normal fluoresent lamps.