An examination of the shadow quality in lighting

In illumination desings, the shadow quality theme is very important because of to obtain the visual comfort requirements and the esthetic that hope to create and accent the architectural properties. `Sharpness and softness? that one of the two different qualities of the shadow is concerned with perceiving or not perceiving the shadow area borders. `Lightness and darkness? is the second properties of the shadow and concerned with the difference of luminance between the lightness area and the shaded area. In this study one of the theme of illumination quality discussed in two groups as sharpness-softness and lightness-darkness and determined the factors which affected them and examined with the samples. Sharpness and softness of the shadow is defined, graded by sensation size that aimed at perceiving the size of the surface. Determined the factors which affected sharpness and softness, affect to the shadow is determined by geometrically. In indoor spaces, illumination distribution property of the different sharpness and softness shadows that formed for certain situations is judged and searched. Illumination distribution determined with illuminance account and one of an illumination program in computer, and compared with the degrees of sharpness and softness which founded by geometricall calculation. Lightness and darkness of the shadow is defined, and graded by the difference of luminance between the shaded area and the lightness area. In indoor spaces, illumination distribution property of the different lightness and darkness shadows that formed for certain situations is judged and searched and also the affects of reflectance of the iner surface to the lightness and darkness of the shadow is examined. The affect of factors like size and the number of the primary light source, size of the obstruction, reflectance of the secondary light source to the shadow quality examined by various samples and founded results are compared and judged. Keywords: Shadow quality, umbra, penumbra, sharpness and softness, lightness and darkness.