Abstract
In order to find fundamental data of the relation between required background luminance and the visual objects-letters and characters printed on paper according as their sizes, kinds, the number of their strokes and their groups as sentences, an experimental study was made by using Apparatus (Fig. 2) as the main device, and Visual Objects (Ex. Fig. 1). And the study was made to obtain the difference of visibility in the case of Landolt Ring Targets and the above-mentioned visual objects. In addition, this study purports to set up a scale for easiness of reading letter and characters. In this experimental study we used, as the standard printing type based on Tables 2〜3, 8-point "mincho" Chinese characters of 8 strokes printed in black on "chushitsu" paper. Figs. 5〜6 show the relation between threshold background luminance and the kinds, sizes and the number of strokes of letter and characters printed separately and groups. Figs. 8〜9 show the relation of visibility between Landolt Ring Targets and the printed matter in question. Figs. 13〜16 are the results of the experiments to set up a scale for readability. As the result of the measurement of the readability, we obtaind the Optimum Level of Illumination being 500〜1500 lx.
