Working areas and room surfaces
Illuminance for surfaces in a space should be correct in relation to illuminance on the working plane to conform to the luminance ratio requirements in the standard. For example, when using low-luminance luminaires and downlights there is a risk of the top of the walls and ceiling being too dark.
Ceiling with indirect lighting
With indirect lighting the average luminance on the ceiling should not exceed 500 cd/m². Within limited areas of the ceiling, a maximum luminance of 1500 cd/m2 is acceptable. The gradient or luminance transition must not be overly sharp so that the lighting in the ceiling is not perceived as distracting and uneven. Luminance uniformity (Lmin/Lavg ) should not exceed 1:10.