Discomfort glare: What do we actually know?

Glare models were reviewed with an eye for missing conditions or inconsistencies. Ambiguities were found relating to when to use small source versus large source models and as to what constitutes a glare source in a complex scene. Also, there was surprisingly little information validating the assumed independence of the factors driving glare. A barrier to progress in glare research is the lack of a standardized dependent measure of glare. The glare models were inverted so as to predict luminance and to compare model predictions against the 1949 Luckiesh and Guth data that form the basis of many of them. The models performed surprisingly poorly, particularly with regards to the luminance-size relationship and additivity. Evaluating glare in complex scenes may require fundamental changes to the form of the glare models.