Abstract
The intensity of light which the navigators actually feel from the background light differs depending on the brightness of the light source, as well as on the length of the background light spreading in the shape of a belt on the horizon, and it is also considered to vary with the direction of visual line of the navigators trying to find the navigatianal aids or signals, etc. For such reason, indoor experiments were conducted concerning the sensitivity distribution in the horizontal direction of eyes for the light, and based upon their results, a study was made about the relation with the 20°visual field. As a consequence, the measuring value by means of a drightness meter of 20°visual field, which was obtained hitherto as a relative value, could grasp quantitatively the sensitivity distribution of eyes, so that it has become possible to convert it into the absolute value. Furthermore, as a result of having grasped quantitatively also about the effect of lamplights around the visual field, we could find there exists something that cannot be ignored from the view point of navigation safety.
