Lightness Perception of Fabrics Under Non-uniform and Uniform Lighting Conditions

Abstract

The overall lightness of the whole surface of a fabric under non-uniform and uniform lighting conditions was investigated. In the experiment, the perceived lightness of the bright, dark, and whole area of pieces of glossy and matte fabric placed on a pseudo-sine-wave board under different combinations of directional and diffused lights was measured by matching the lightness to a reference grayscale placed in the matching box with a diffused light. The perceived lightness of the bright and dark areas could be expressed with a linear function of the logarithmic luminance of each area for both the glossy and matte fabrics. The perceived overall lightness under the non-uniform lighting conditions with directional light was close to that of the dark area with no significant contribution of the lightness of the bright area. This is consistent with the previous study which showed the elimination of highlights in the lightness judgment. However, contribution of the bright area was not nothing because it raised the perceived lightness value about 1.2 times higher than that of the dark area. On the other hand, the overall lightness under the uniform lighting condition with diffused light only was estimated by the weighing sum of the perceived lightness of bright and dark areas. Further investigation into the effects of spotlight size, its luminance, luminance contrast between the bright and dark areas, and the glossiness of fabric is necessary.