MUSCULAR TENSION RESULTING FROM GLARE

An effect of glare in a situation requiring critical visual effort was appraised by recording muscular tension developed in the fingers. Measurements of muscular tension were made for intensities of illumination of 1 and 5 footcandles, respectively, without preventable glare and at an intensity of illumination of 5 footcandles at the test-object and 5 footcandles of preventable glare at the eyes. The results indicated that the effects of the glare-source were comparable in magnitude to the effect produced by decreasing the level of illumination from 5 footcandles to 1 footcandle. The discussion emphasizes the far-reaching effects of glare upon the human seeing-machine.