The influence of illumination level on prolonged work performance

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Abstract
The paper discusses the effects of illumination ieveis on prolonged work performance. Measurements have been taken of speed, accuracy, fatigue, vigilance, critical flicker frequency, liminal brightness increment and subjective responses from subjects working for two-hour periods at fixed illumination levels. The results, from fourteen subjects, revealed that illumination level had little effect on accuracy or vigilance. The predominant effect was on the speed of working. It was found that after an initial practice period, a decrease in speed of working and an increase in the variability of speed of working occurred at low illumination levels. These fatigue effects on performance were supported by an adverse change in a physiological measurement, namely the liminal brightness increment, after work at the lowest illumination level. The subjective results were in reasonable agreement with the performance results. It is concluded that there existed an optimum range of target luminances (147-344 cd m-2 ) over which superior prolonged performance of the experimental task could be obtained.