Visual task performance and perceptions of lighting quality under flickering illumination

Even when not directly visible, flicker from light sources at frequencies exceeding 100 Hz can influence perception through stroboscopic effects. Three experiments were conducted to evaluate the impacts of flicker varying in frequency and modulation depth on visual performance, comfort and preference. In one experiment, subjects performed a numerical verification task under flickering illumination from 100 to 1000 Hz and from 25% to 100% flicker. Error rates were lower under higher frequency and lower flicker modulation and visual comfort was slightly higher. In the second experiment, subjects preferred higher frequency and lower modulation than 100 Hz, 100% flicker. In the third experiment, subjects equated perceived quality from illumination with higher frequency or lower modulation flicker when the illuminance was reduced by about half, relative to 100 Hz, 100% flicker. The results were consistent with a recently published model of the perception of stroboscopic effects.