Interaction of screen distances, screen letter heights and source document distances

An experiment was conducted to investigate the main and interaction effects of screen distances (600 mm and 900 mm), screen letter heights (for visual angles of 16, 20, and 30 minutes of arc), and source document distances (same as the screen distance and closer than the screen distance) on visual performance and subjective preference in text proofreading tasks. Thirty subjects in different age groups participated in the experiment. The experimental results revealed that the subjects' performance improved from the letter height of 16 minutes of arc to the letter height of 20 minutes of arc for the 600 mm screen distance, but from 20 minutes of arc to 16 minutes of arc for the 900 mm screen distance. The subjects generally preferred a screen distance slightly higher than 600 mm, a letter height at the 22 minutes of arc, and a small difference between the visual angle of screen letters and the visual angle of source letters.