Colour rendition refers to the quality of the reproduction of colours under a given illumination. The degree of colour distortion is indicated using the colour rendition index Ra and/or the colour rendition grading system. A comparative light source with continuous spectrum serves as a reference light source, whether this be a temperature radiator of comparable colour temperature or the daylight.

Colour rendition


Ranges of the colour rendition index Ra for different lamp types


To enable the colour rendition of a light source to be determined, the chromatic effects of a scale of eight body colours viewed under the type of illumination being scrutinised and also under the reference illumination are calculated and related to each other. The resulting quality of colour rendition is expressed in colour rendition indices; these can relate both to the general colour rendition (Ra) as an average value or to the rendition of individual colours. The maximum index of 100 signifies ideal colour rendition as experienced with incandescent lamp light or daylight. Lower values refer to a correspondingly worse colour rendition. Linear spectra of light lead to good colour rendition. Linear spectra in general lead to a worse rendition. Multiline spectra are composed of several different linear spectra and improve the colour rendition.

Colour rendition index

Guide
The comprehensive Guide provides suggested solutions for different lighting tasks.

Basics

Perception as the basis for lighting design

Designing with light

Light makes objects visible and influences the mood of a room

Indoor lighting

Principles and methods of indoor lighting

Outdoor lighting

Principles and methods for outdoor lighting

Lighting control

Dynamic lighting effects and optimisation of energy usage

Lighting technology

Lamp and luminaire technology

Simulation and calculation

Methods, data and examples for visualisation

Glossary

back