Abstract
Purpose. It was shown previously that a peripheral glare source reduces the brightness of a foveal test. This reduction of brightness cannot be explained by a luminance match. In this work we performed an experiment to test the hypothesis that our brightness evaluation task is affected by lightness intrusion. Methods. Using a magnitude comparison method we evaluated the brightness of a foveal patch and its near surround, when they are presented simultaneously to a transient glare source, for a wide range of patch luminances. The stimuli were in the mesopic range and two glare levels were used (30 lx and 60 lx) with the glare source located 10 deg away from the line of sight . Results. Results show that brightness of both the patch and the surround are reduced by the presence of the glare source. We found that equating local contrast ratios can explain our results if a unique veiling luminance is added to the stimulus for the whole patch luminance range. Conclusions. In coincidence with brightness literature, this finding indicates that brightness evaluations under glare condition have an intrusion of lightness that shift the brightness judgement from a luminance match to a local contrast ratio match.