The luminance distribution, (or better distribution of brightness within the field of view), is an extremely important criterion of lighting quality.
The other quality criteria (with the exception of color) are in fact subordinate to luminance distribution. Take lighting level, for example, a sheet of white paper on a dark desk has a higher luminance than the desk, but the illuminance on paper and desk is the same. The luminance difference is due to the difference in reflectance between paper and desk. In the case of glare, this is simply a case of disturbing high luminance in the field of view. The spatial distribution of the light creates areas of light and shadow, which is once again simply a luminance distribution. (Fig 2, 3 & 4)
Fig 2: Luminance contrasts that are too low result in a dull and flat visual scene with no point(s) of interest.
Fig 3: Luminance contrasts High are distracting and give rise to adaptation problems for the eye when changing from one visual target to another
Fig 4: Well-balanced contrasts result in a harmonious visual scene, which gives satisfaction and comfort.
Brightness contrasts should be neither too large nor too small
The requirement that the brightness distribution should be satisfactory suggests that an assessment of the quality of the lighting is necessarily subjective. In the case of an interior, a good lighting design cannot compensate for a bad interior design. Minimal reflectance of ceiling, walls, curtains, furniture, etc., are inappropriate, as visual satisfaction with the surroundings can hardly be achieved. Lighting can improve and enhance the situation, but the ultimate result will be of a rather poor quality. As a general rule, in interior situations it can be taken that for satisfactory results, the luminance contrast ratio (L high / L low) in the field of view should not be larger than 3 and not smaller than 1/3.