Color Rendering Index

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A measure of the ability of an illumination system to produce a uniform spectral energy envelope. On a scale of 1-100, a light with a perfect Color Rendering Index (CRI) of 100 would illuminate all colors evenly and without distortion. Most light sources, however, emit stronger radiation at some wavelengths and thus distort the appearance of colors. An incandescent lamp, for example, emits small amounts of blue and green light relative to red which results in muted blue tones. Some light sources and their CRI values are:

  • Tungsten halogen (99);
  • Incandescent (92-95);
  • Deluxe cool white fluorescent (89);
  • Daylight fluorescent (79);
  • Deluxe warm white fluorescent (73)
  • Cool white fluorescent (62-66);
  • Warm white fluorescent (52);
  • Metal halide (50); and
  • High pressure sodium vapor (21).

Synonyms and Related Terms

CRI; Ra; Color Rendition Index (sp); Colour Rendering Index (Br.); Farbwiedergabeindex (Deut.)

Resources and Citations

  • Book and Paper Group, Paper Conservation Catalog, AIC, 1984, 1989

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