CRI and colour rendering

CRI describes colour rendering compared with a reference source. The general Ra value is not the whole story, but it is a useful filter for kitchens, wardrobes, colour work and displays.

Practical example

A 20 m² room with a 150 lx target needs 3,000 lumens reaching the plane. With UF 0.65 and MF 0.80, the sources need about 5,769 lm. Six 1,000 lm fixtures give an estimated 156 lx.

Limitations

The simplified model does not know fixture intensity curves, individual surface reflectance, obstacles, glare or uniformity. A construction-ready design requires photometric data and suitable software.