Effects of Viewing Distance and Local Illumination on Projection Screen Visual Performance

The main purpose of this study is to evaluate the viewing distance and local illumination effects on visual performance while working with a projection screen. Digital projectors have become more popular. However, studies on visual performance using a projection screen are rare. Viewing distance (3, 6, and 9 m) and local illumination (75 and 450 lux) were the independent variables. Each experimental trial took 40 min, including a 10-min proofreading task and a 30-min film watching task. The identification rate for the proofreading task and the attention rate for the film-watching task were collected. The results indicated that viewing distance had a significant effect on the identification rate (p=0.04). A reduced identification rate tendency was found with increasing viewing distance. A significantly higher attention rate (p=0.032) was found at the local illumination of 450 lux compared to that of the 75 lux. We suggest that (a) a shorter viewing distance (correspond to 25~50 min arc of visual angle) is suitable for performing text-reading on a projection screen; (b) if the visual tasks with a projection screen mostly contain video and voice, the viewing distance will have little effect on performance; and (c) the local illumination on the audience's work area should be around 450 lux while watching a film with a projection screen. Actual or potential applications for this research include recommendations for proper viewing distance and local illumination for projector users.