CIE x048-PO47 PDF

Architects and users frequently use window coverings, such as frosted glasses, shoji screens, and lace curtains to create high quality of light. This kind of light is sometimes called soft light, and most people feel that it is required in residential spaces. However, the term soft light is somewhat vague, and we do not accurately understand what is the soft light and how we can create it. The aim of this research is to derive a physical indicator of ambiguity of brightness-darkness boundary, which is one of factors for judging the softness of light. We conducted a subjective experiment with 53 evaluation items including the ambiguity of brightness-darkness boundary in various actual daylighting spaces. It was found that ambiguity of brightness-darkness boundary, was not highly evaluated when the average value of the luminance change rate on the wall is high.