Evaluation of Glare

The basic formula for the evaluation of glare discomfort is reviewed and some of its many limitations discussed. Cross-checks undertaken during the last few years at the Building Research Station show that nevertheless it still serves a valuable purpose for practical lighting engineering, provided too great a precision is not sought. The additivity of glare is discussed, in relation to the saturation characteristics of the adaptation mechanism. It is suggested that the simple addition of the glare effects of a number of sources can never give a "true" solution, but that is often yields a result of adequate precision for most present-day lighting problems. The greatest need for further research is in the study of the discomfort caused by very large sources of moderate luminance, such as occur in daylighting or in the use of "overall" ceiling lighting.