Effect of Projection Size of Partition Frame on Separation of Two Recognized Visual Spaces of Illumination

Abstract

The size of the recognized visual space of illumination (RVSI) is a concept for expressing the perception of brightness of a space recognized by an observer. If he/she recognizes the space as being brightly illuminated, the size of RVSI is said to be large. The apparent lightness of an object placed in the space is determined relative to the size of the RVSI. The size is controlled by changing the illumination level of the space. It can also be controlled by changing the lightness of the interior of the space even if the illumination is kept constant. Then the apparent lightness of the object becomes lower with an interior having high lightness. Two miniature rooms in the depth direction from a subject, were illuminated at the same illuminance level, but the front room had walls, floors and furniture with lower lightness than the back room. It was expected that the RVSI of the front room would be smaller in size than that of the back room. The two rooms were separated by a partition frame projecting from the side walls. In this paper the effect of the projection size of the partition on the size change of RVSI at the boundary of the two rooms was investigated by measuring the apparent lightness of a test patch along the depth of the rooms for three different projection sizes. It was found that the effect of projection size was not significant and that the separation into two RVSIs was mainly achieved by interior lightness.