Two experiments were conducted: one to determine whether a digital still camera can be used to measure luminous contrast with the same degree of accuracy as that obtained by using a photometer, and the other to compare the visibility performance of a digital still camera and the human eye. The digital still camera used in this study, Canon EOS-DCS3, is one of the highest quality cameras currently available. The results of the first experiment indicated that an image taken by the digital still camera can provide the luminance value as a function of exposure value. The second experiment was conducted on a test site used for driver's license testing in Sapporo. Seventy subjects participated in the experiment. Each subject was asked whether she/he could detect the targets on a road. The background luminance and contrast were estimated using the images taken by the digital still camera. The detection level decreased as the contrast of the targets decreased. In most cases, the invisible detection level fell well below Blackwell's threshold contrast of the human eye. Based on the results, it is concluded that a very high-quality digital still camera can be used to accurately evaluate the visibility of targets on a road. (A*)
Abstract