Color Rendering Index (CRI) is the measurement of how faithfully a light source reveals the colors of objects. The index range is from 0 to 100. The higher the CRI, the better the color accuracy. CRI is an important lighting feature for skin tones, decorating, merchandising and more.
For example, lighting used in a grocery or clothing store should have a very high CRI (80 to 100). Afterall, how appealing is greenish steak or magenta shoes that are actually red when you bring them home?
Incandescent lights show all colors well, so they have high CRI’s. Low-pressure sodium vapor lamps have poor CRI’s, near 0. This is because their light is mono-chromatic—almost all light is at one frequency. That frequency’s color is the only color those bulbs illuminate well.