Spectral tuning to increase spatial brightness: effect on visual performance, eye fatigue and comparison of 5-s and 20-min exposure durations

An experiment was conducted to evaluate the effect of a spectral power distribution (SPD) optimized to increase spatial brightness compared to one approximating a typical blue-pump, phosphor-converted LED (YAG:Ce). Chromatically and luminance-adapted participants completed a reading task, visual search task, numerical verification task and provided ratings for brightness, vividness, warmth and preference over the course of approximately 20 min for each of four lighting conditions (two SPDs by two illuminance levels (nominally 250 lx and 500 lx)). As a final task, the participants chose the brighter SPD between the two SPDs that were alternated every 5 s. In alignment with a past experiment where participants provided ratings after viewing 60 stimuli for about 20 s to 30 s each, the brightness-optimized SPD was rated as brighter, more vibrant and more preferred than the PC-like SPD. When evaluated as a choice in a rapid sequential presentation, the brightness-optimized SPD was chosen as brighter than the PC-like SPD 28 out of 30 times. There was not a statistically significant change in spontaneous blink rate (an indicator of visual fatigue) or blink duration, nor any difference in glare, eye fatigue or eye discomfort. Results for visual performance were mixed.