Analyzing the effects of illuminance variations on occupants’ visual perceptions to determine permissible dimming controls of lighting in small offices

This study investigated the influence of illuminance variations on visual responses to suggest permissible dimming ranges of lighting control systems in office. A series of experiments were conducted with 33 participants for workplane illuminances of 500 lx, 650 lx, and 800 lx in real office environments under five levels of illuminance variations. Paper-based and computer-based reading tasks were conducted for each condition. The results indicated that none of the constant workplane illuminance caused visual discomfort or dissatisfaction. Illuminance variation was perceived most strongly under the workplane illuminance of 500 lx, and the effect of illuminance variation on the perception of glare was the weakest under the workplane illuminance of 800 lx. As the variation ranges in illuminance increased, the degree of perceived visual satisfaction diminished stably compared with the degree of perceived glare and illuminance change.Strong linear relationships existed between illuminance variation and visual comfort. The maximum permissible ranges of illuminance variations that maintained visual comfort were 150.0 lx, 135.2 lx, and 121.9 lx for paper-based tasks and 126.9 lx, 115.8 lx, and 80.8 lx for computer-based tasks when the workplane illuminance were 500 lx, 650 lx, and 800 lx, respectively. The perception of eye fatigue was a common factor that affected the perception of visual comfort when illuminance variations occurred under the three workplane illuminance conditions. The influences of glare, visual stimuli, and eye fatigue were the factors that degraded the perception of visual comfort.