The effect of glare on visual performance and visual perception

E M COLOMBO, R C AGUIRRE, J F BARRAZA

Regensburg, Alemania

Congreso; 31th Annual Eurpean Conference on Visual Perception - ECVP 2009; 2009

University of Regensburg - Perception

The presence of a peripheral glare source produces a darkening of the perceived stimulus that could be associated to an equivalent variation of luminance. This reduction of luminance should lead to a predictable impairment of the visual performance. To check it we performed two experiments measuring reaction time (RT) as a function of the contrast (C) of a sinusoidal grating presented foveally with a luminance of 0.14cd/m2. The first experiment was carried out with three glare illuminances (EG=0, 15, 60 lux, q=10°) and the second experiment covered the appropriate stimulus luminance (L) range such that results from both experiments could be compared. Both sets of data were adjusted by using the equation RT=RT0+k(1/C). Results show that k increases with increasing Eg and decreasing L. We calculated the equivalent luminance for each level of glare by comparing the values of k. We found that the darkening effect of glare measured by means of visual performance corresponds to a reduction of luminance of around 10 times. These equivalent luminances are much larger than those determined by measuring brightness perception. This suggests that performance and perception may be reflecting very differently the darkening effect of glare.