OPTIMAL TEXT-BACKGROUND LIGHTNESS COMBINATIONS OF TABLET DEVICES FOR VISUAL COMFORT UNDER A WIDE RANGE OF ILLUMINANCE LEVELS

The psychophysical experiment was carried out to investigate how illuminance level affected the visual comfort for e-reading on a tablet device. 44 Asian observers between 19 and 25 years of age (mean = 21.5, SD = 1.2) participated in the experiment, comprising 20 observers evaluated the visual comfort experiment under dark condition, 300 lx and 3 000 lx and 24 observers evaluated the visual comfort experiment under 150 lx, 1 500 lx and 15 000 lx. The experimental results show that the visual comfort interval scale below 1 500 lx conditions (i.e. Dark, 150 lx, 300 lx and 1 500 lx) were similar to each other, but not to the visual comfort interval scale above the 1 500 lx conditions (i.e. 3 000 lx and 15 000 lx). For the same lightness difference between text and background, the observers’ judgements show that they felt more comfortable to read the document using white background than the document using black background under high illuminance level.