抄録
By using the apparatus (Fig. 1), Landolt Ring targets (Figs. 5〜6) and circular targets, an experimental study was made for lighting plan to find fundamental data of minimum perceptible contrast and visual performance curves. In this experiment not only white but also blue, red and green light were used. The result in shown in Figs. 7〜11. From the result of the measured mean log-value of each observer, both the minimum perceptible contrast and standard visual performance curves were found. Under white light (Fig. 12) raising the background luminance to approximately 1000 cd/m^2 improved the visual performance. However, an increase above this level up to 10000 cd/m^2 had only little effect upon visual performance, and the glare occuring over 10000 cd/m^2 suddenly increased the minimum perceptible visual angle. Moreover, from over a background luminance of 1000 cd/m^2 the observers started feeling pain in their eyes. From this result, it was observed that in order to get a better visual performance it is better to keep the background luminance under 1000 cd/m^2. From a comparison of the visual acuity of each observer, it can be seen that for bad visual acuity a higher background luminance is required (Fig. 13〜14).
