Glare limitation · reflected glare
Reflected glare and direct glare are caused by bright surfaces in the field of vision and are considered to be disruptive factors.
The term reflected glare is used to describe irritations that are triggered, for example, by lamps, luminaires or windows with high luminance. This occurs particularly frequently on wet asphalt roads, glossy paper or on display screens. The occurrence of such disruptive factors can be avoided with the right choice of luminaires, lamps and their arrangement in buildings or outdoors.
In order to calculate reflected glare on horizontal shining surfaces, the CRF (Contrast Rendering Factor) is determined using suitable software. As a rule, an office has a minimum CRF value of 0.7, and when glossy materials are being used, a higher value must be assumed. Besides the reduction in luminance levels reflected in glossy surfaces (e. g. screens), it is also possible to change the arrangement, thus minimising the reflective surface. Depending on the degree of direct or reflected glare, physiological or psychological glare may occur. Physiological glare is accompanied by problems in perception caused by a reduction in visual performance. The recognition of shapes and depth perception are made more difficult.
Psychological glare, on the other hand, is not quantifiable using technical means. Only the subjective sensation of the individual is decisive and opinion-forming. Symptoms may be discomfort, insecurity or fatigue. To ensure that such effects do not occur in the first place, it is good policy to avoid glare, particularly above the horizontal of the field of vision.
In indoor illumination, psychological glare is determined by the UGR method (Unified Glare Rating). This is based on a glare formula which takes account of all luminaires in the system that lead to the glare impression. To allow a uniform evaluation to take place, UGR tables provided by the luminaire manufacturers are used.
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