Direct glare is caused by too high luminance, i.e. lights or illuminated surfaces in the field of vision that are too bright. Causes can be unsuitable or incorrectly installed lights, sunlit surfaces or insufficiently glare-free lights.
Psychological blinding
Bright surfaces in the field of vision can be disturbing without immediately reducing the visual performance. This blinding is called psychological blinding. If the disorder is prolonged, it can lead to increased visual strain and has unfavorable effects on general well-being, work performance, motivation and the ability to concentrate. Fatigue increases. Psychological blinding must therefore be limited.
Physiological glare
Physiological glare or fading, on the other hand, causes an immediate reduction in visual performance. If psychological glare is limited, physiological glare generally does not occur. Psychological blinding is influenced by the following variables:
- Luminance of the glare source (e.g. visible luminous surface of a lamp)
- Size of the glare source seen by the observer
- Location of the glare source in the field of vision
- Ambient luminance
The assessment of psychological glare from lights is carried out using the UGR Method according to DIN EN 12464-1. The smaller the UGR value determined using this procedure, the lower the psychological blinding. The UGR tables from the lighting manufacturers' documentation can be used to check lighting systems. In rooms with computer workstations and office workstations, the UGR value must not be greater than 19, regardless of the lighting level.
