Effects of Contrast and Character Size upon Legibility of Japanese Text Stimuli Presented on Visual Display Terminal

We examined effects of contrast and character size upon legibility of Japanese text stimuli presented on visual display terminal (VDT). In the experiment, three different character sizes were employed and the text stimulus was presented under a variety of conditions where contrast between the text and the background changed. Reading speed and the rate of readable characters were measured. Subjective rating for legibility was also evaluated. Results showed that legibility increases with luminance contrast for all character sizes examined here. A strong correlation was found between the subjective rating index and reading speed.