UGR, Unified Glare Rating, is a psychological metric used by the International Commission on Illumination to measure the subjective response of light emitted from lighting fixtures in indoor visual environments that cause discomfort to the human eye.
The original industrial and civil lighting design standard specifies the direct glare of indoor general lighting, which is limited according to the brightness limitation curve. This limitation method is only for the glare of individual lamps, and cannot characterize the total glare effect produced by all indoor lamps. Therefore, CIE proposed the formula of Uniform Glare Rating (UGR) based on the synthesis of glare calculation formulas from various countries. Applicable to the general lighting design of simple cube-shaped rooms, the lamps and lanterns are evenly and equally spaced, the lamps and lanterns are double symmetrical light distribution, the observation position is generally at the midpoint of the longitudinal and transverse walls, the line of sight is horizontal towards the front observation.
Glare is one of the main factors affecting the health of the light environment. Although the human eye can adapt to luminance in a range of about 14 orders of magnitude, after a period of adaptation to a certain brightness level of the visual field, the effective area of luminance to which it can adapt will be reduced to 4 to 5 orders of magnitude, and other objects or light sources above that area will produce glare. Currently, there are many different models for evaluating glare metrics and methods, using different evaluation algorithms depending on the specific lighting application environment. For example, in road lighting with commonly used threshold increments (TI) to evaluate disabling glare, indoor workplaces in commonly used uniform glare index (UGR) to evaluate uncomfortable glare, in addition, the index to evaluate uncomfortable glare are glare index (GR), British glare index (BGI), CIE glare index (CGI), etc.
The UGR can only be obtained in a calculated way, not from a light distribution file such as the IES to determine whether there is glare. This is the result of the relative relationship between the luminous surface of a light fixture and the user's or observer's viewpoint, position, and background environment. In places with special requirements for glare, we recommend the use of anti-glare downlights.
