Influence of light fluctuation on occupant visual perception

This study examines visual perception influenced by fluctuating light levels in order to determine acceptable tolerance ranges for light changes. This study also investigates whether the change of light levels significantly impairs the performance of computer-related reading tasks as a surrogate for a productivity test. Annoyance tests were conducted under a variety of fluctuating illuminance levels controlled by a direct lighting system in a full-scale mock-up office space. Healthy 19 female and 17 male subjects whose ages ranged from 20 to 45 years participated in the tests. Visual annoyance did not significantly correspond to illuminance variation, but it differed according to the task illuminance that subjects were initially adapted to. The higher desktop illuminance the subjects initially had, the less visual annoyance they reported when equal amount of light levels varied. When automatically controlled dimming systems that cause frequent light fluctuation are used in an office space, the task illuminance should not be lower than 650 lx, and the maximum fluctuation of illuminance should be controlled within 40% of the task illuminance in order to reduce visual discomfort. Multiple linear prediction models showed that the feelings of eye fatigue, distraction, difficulty of seeing letters, and annoyance were significantly influenced by fluctuating light levels. It was also found that the fluctuation of illuminance under two illuminance conditions tested in this study did not significantly influence reading task performance.