Abstract
This paper treats the research on the shadow characteristics under such conditions as both the light source and the shadow caster have various geometrical shapes. The shadow casting performance of a horizontal disk is described in several typical light sources—horizontal and vertical, each taking the shapes of a straight line, a rectangle, a square and a circle. A digital computer analysis shows specifications of the umbral, penumbral and ultraumbral regions on the illuminated plane. First, the methods for numerical calculation of the illuminance and the shadow factor within the shadow are explained briefly. Second, with a horizontal disk fixed as a shadow caster, the shadow characteristics of various light sources kept in several positions are shown. Third, those results are compared. Finally, the position and shape of the light source usefull to reduce as much shadow as possible are mentiond.
