Current knowledge of visual performance

Threshold, supra-threshold, and physiological measures of visual performance are compared. Present physiological measures are of little use in visual performance research, but threshold and supra-threshold measures can be usefully used. The effects of illuminance, disability and discomfort glare, luminance distribution and colour on visual performance are then reviewed. Illuminance has the most important effect. The only other important variable is that of veiling reflections. The effect of the operational variables of subjects' age, visual capability and the work characteristics are examined and indicate that human factors are more important than physical factors in their effect on visual performance. In the final section the synthesis of existing knowledge of visual performance, presented in CIE Report No. 19, is explained and suggestions made for extending and examining its validity and application. Some general pointers for the direction in which future research might progress are given.