Glare models developed for electric lighting conditions are not applicable to daylight
situations. This report summarizes the daylight glare prediction models which were
confirmed by independent studies.
The cause of the sensation of discomfort glare appears to be a compound of two effects:
contrast effect and total-amount effect. Total-amount glare is caused by the total
amount of light reaching the eye, whereas contrast glare is caused by extreme
luminance contrasts in the field of view. The glare prediction models are divided into
three types: contrast-based, total-amount-based and hybrid models. The practical
problems of the models, e.g. definition of the glare source, subjective rating scale, and
applicability and limitation of the models are discussed. Moreover, factors other than
the four main variables to consider (glare source luminance, background luminance,
solid angle of the glare source, position index) are summarized. It is important to
consider the limitations and conditions for which each of the prediction models is valid
to select the most appropriate one based on the specific situation.