Duration of Afterimage Disability After Viewing Simulated Sun Reflections

Abstract

A scene was simulated of an automobile driver's view through his windshield. It contained a roadway, an identification target consisting of a Landolt C in various orientations on the road 96 m ahead, and a glare reflection of the sun arising from the direction of the driver's windshield wiper arm. The product of luminance times area of each of the four glare sources employed was about 0.1 of the maximum implied in the Federal Safety Standards. The target required a visual acuity of 20/40 on the Snellen scale, equal to that imposed by driver license requirements. After being exposed for realistic intervals while looking directly at the glare source, the duration of the interval required by thirty-five observers for identification of the target orientation was measured. Averages showed that the increase of identification time over that required after no glare exposure varied from 0.8 sec to 2.7 sec. Reduction of apparent area of the glare source reduced afterimage disability more than did reduction of intensity.