The UGR value is calculated according to a method presented by the CIE in 1995 (source: Technical Report 117
). As a system-related assessment, the UGR method takes into account all luminaires in the lighting installation that contribute to the glare. The calculation rule totals the glare effect of all light sources based on their average luminance
, spread and position in relation to the viewing direction. It also considers the dependence of the eye's sensitivity to glare on the background luminance. Logarithmic scaling (lg) and a pre-factor of 8 give a value range from 10 (lowest probability of glare) to 30 (very high probability of glare). A computer simulation makes it possible to calculate the UGR value at any location in the room for any direction of view.