The Answer
The Short Answer
CRI is one useful comparison point when colour fidelity matters, but it should not be treated as a complete score for light quality. Two products with the same CRI can differ in spectrum, saturated-colour rendering, glare, flicker, distribution, and consistency. Match the requirement to the task and, for colour-critical work, assess more than Ra alone.
The Full Explanation
How to Read the Number
DOE guidance describes CRI 80 as a common minimum recommendation for interior lighting and 90 or above as excellent colour fidelity, but the appropriate threshold depends on the application. Colour-sensitive tasks can justify a higher requirement than circulation or storage areas.
What CRI Does Not Tell You
CRI is based on an average of test colours and has known limitations, especially for some saturated colours. CIE now recommends reporting newer colour-fidelity information alongside CRI during the industry's transition, so a single Ra value should not be the only basis for a colour-critical specification.
How to Compare Products
Check the declared CRI or Ra, correlated colour temperature, lumen output, dimming compatibility, and any fuller colour metric the manufacturer supplies. An omitted CRI is missing information; it is not proof of a particular score. For important applications, compare samples in the intended space.
Related Questions
Sources
- 1Colour Rendering Index Definition
International Commission on Illumination
- 2LED Basics
U.S. Department of Energy
- 3CIE Position Statement on Colour Quality Metrics
International Commission on Illumination