Abstract
Visual acuity of 8 subjects was measured as a function of stimulus luminance. Although an extensive literature exists on the correlation between visual acuity and luminance, there are still gaps in particular for light symbols at different luminances of the environment. Since these data can be efficient and useful in studies of the legibility of traffic signs this study was carried out. High contrast causes irradiance effects for light symbols on a dark background if the stimulus luminance is higher than 20 cd/sq m. No differences in the results were found in any condition with long presentation times between light symbols on a dark background and dark symbols on a light background.