Colour rendering index
The colour rendering index (CRI) describes the colour fidelity of a light source. For this purpose, the relative colour temperature of the light source to be measured is first determined. Then eight standard colours (see illustration) are first irradiated by an ideal black body of the same temperature and then by the light source to be measured. If none of the standard colours change in appearance, the light source is given a colour rendering index of 100 (the CRI is measured on a scale of 0 to 100 percent). The greater the colour changes, the lower the value for the colour rendering index, the higher the value, the more suitable the light is for correctly representing the individual colours.
A high colour rendering index is particularly important for applications where the recognition of details is important. Examples include the use of “high-CRI” searchlights in rescue operations or as cabin light for quality assessment in paint shops.