A lower colour rendering index for lamps often results in a higher luminous efficacy and vice versa. In high halls, lamps with elevated luminous efficacy, e.g. high-intensity discharge sodium vapour lamps, are often used for economic reasons. These, however, only have a colour rendering index between 40 and 60 (see also chapter "Light source, luminous efficacy").
In exceptional cases, EN 12464-1 permits the use of these lamps, however continuously occupied workstations and safety sign locations should be provided with elevated colour rendering according to table to table using additional lighting.
When using LED luminaires, this problem can be mostly avoided. They are available with good colour rendering and simultaneous high luminous efficacy. High efficiency as in addition to lower maintenance requirements also make them economically attractive.