The UGR method (Unified Glare Rating) is an international index presented by CIE in publication 117 and is used to evaluate and limit the psychological direct glare from luminaires. Contrary to previous methods where the glare was rated using the luminance values of a single luminaire, this method calculates the glare of the entire lighting installation at a defined observer position. According to DIN EN 12464, the UGR reference value is provided for a standard room. An exact calculation of the UGR value at a defined observer position in a room is possible with modern lighting design programs. The lower the UGR value, the lower the glare. Where the luminance is < 1000 cd/m2, additional data is provided on the elevation angle, either 65°, 75° or 85°. This is the critical angle above which the luminaire has an all-round luminance of 1000 cd/ m2.
