CRI (Colour Rendering Index)
A score (0–100) for how accurately a light source shows colours compared with natural daylight.
Technical definition
CRI (Ra) is a CIE-defined metric comparing a light source's rendering of a standard set of test colours against a reference illuminant of the same colour temperature.
Common confusion
CRI and colour temperature measure different things — a light can be a flattering warm colour temperature but still have poor CRI, rendering colours inaccurately.
Example
Many cheap LED bulbs have lower CRI than daylight or high-quality bulbs, which is part of why paint samples can look 'off' under them.
Why it matters
A low-CRI bulb is a common, under-recognised reason a paint colour looks different at home than in a shop or outdoors.
Related terms
Sources
- CIE (International Commission on Illumination) publications — CIE