Explanation in detail
The color rendering index is a photometric quantity used to determine the color impression of an illuminated object. It is a unit-less reference index. Sunlight serves as the reference. The index describes the quality of the composition of the white light of a light source.
This allows to make a statement about the quality of the reproduced colors. The color rendering index can be used to compare the quality of the color rendering of different light sources.
How is the color rendering index determined?
The color rendering index is independent of the color temperature. このため, a suitable reference light source with identical color temperature is always used to determine the reference index depending on the light source. A black spotlight serves as the reference light source for all color temperatures up to 5000 K. All light sources above are measured with a reference similar to daylight.
In order to determine the color rendering index for a light source, the following 14 test color samples were specified in CIE (1995).
In the test procedure, the secondary spectra from the light source are measured and compared with the reference light source. The color rendering index is then calculated from the individual deviations (difference between artificial and natural light sources). For this purpose, the mean value is calculated from the values TCS01 to TCS08.
Color rendering index for LED lights
When switching to LED lighting, often only brightness and color temperature are taken into account. The color rendering index is not very tangible for many people and is therefore hardly noticed. The CRI value is another important parameter for good lighting quality, especially in the home.
Our products, LED lightings for refrigerated display cabinets or shelves, CRI are all >80.
