The impact of spectral power distribution on the performance of an achromatic visual task

This experiment tests the hypothesis that light sources that produce smaller pupil sizes ensure better achromatic visual task performance at the same photopic illuminance. Two groups of subjects, one in the age range 18-28 years and the other in the range 61-78 years, performed a Landolt ring task for eight different gap sizes, two different illuminances, and two lamp scotopic/photopic ratios. For both age groups, pupil size was determined by both illuminance and lamp spectrum. The speed and accuracy of performance of the task was determined by the gap size, and to a much lesser extent, by the illuminance. Lamp spectrum had no effect on the performance of the task.