What is the CRI color rendering index?

Color Rendering Index CRI

The color rendering index CRI stands for Color Rendering Index and indicates how well an artificial light source can reproduce the natural color of an object.

This specification has been of interest to consumers since the introduction of energy-saving lamps and LEDs, because unlike conventional incandescent lamps, these cannot reproduce colors as naturally as daylight.

The reference value is the sun or daylight with an Ra value of 100. A spectrometer can measure the reflected light from the test light source and compare it with specified reference values. This results in 8 R-values for different color spectra. The average value is formed from these values and the meaningful Ra value (a here stands for general) of the light source is obtained.

Ra ≥ 90

very good

Ra ≤ 80


Ra < 80

not recommended

Examples of Ra values for different light sources:

  • Incandescent lamp ≈ 100
  • Halogen lamp ≈ 98
  • White LEDs ≈ 70-95
  • Fluorescent lamp ≈ 50-90
  • Mercury vapor-
    High-pressure lamp ≈ 45-50
  • Black light ≈ 0
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