What is Glare?
Glare is a visual sensation caused by excessive and uncontrolled brightness. It is subjective, and sensitivity to glare can vary widely. Older people are usually more sensitive to glare due to the aging characteristics of the eye. There are two commonly considered types of glare:
- Discomfort Glare – the sensation of annoyance or even pain induced by overly bright sources, but not actually stopping you seeing.
- Disability Glare – the reduction in visibility caused by intense light sources in the field of view. It causes a loss of visibility from stray light being scattered within the eye.
The common metric that is used to quantify Discomfort Glare is the Unified Glare Rating or UGR.
UGR is lighting installation specific. The formula requires the knowledge of the position and brightness of each potential glare source. UGR measures the luminance of a luminaire divided by the background of visible luminance from the room. The UGR ranges from 5 to 40. Lower numbers are better and indicate less glare. For example, a low UGR of 10 means the glare is so discreet it will go unnoticed.
Recommended UGR Limits
|Working area||Maximum allowed UGR|
|Industrial work, fine||22|
|Industrial work, medium||25|
|Industrial work, course||28|