Range Normalization in the Luminance-to-Lightness Mapping

摘要

We report strong distortions of the ratio principle using low dynamic range, but highly articulated, mondrian patterns. Our stimulus consisted of two perpendicular planes, meeting at a dihedral corner and viewed in a vision tunnel. Although the two planes were equally illuminated, one plane was covered with a pattern of strictly light gray patches ranging from middle gray (Munsell 4.5) to white (9.5), while the other plane was covered with a pattern of strictly dark gray patches ranging from middle gray (4.5) to black (2.0). The two mondrians had either 5, 25, or 150 patches on each side. In each case, the mondrians appeared differently illuminated, each tended towards a white anchor, and the perceived range of gray shades in each plane was expanded relative to the actual range. Moreover, the amount of expansion was proportional to the number of patches (articulation). In the 25-patch condition, for example, the 5.8:1 actual range of luminance on the lighter side was perceived as an 11:1 range of matched reflectances. On the darker side, 5.2:1 expanded to 10:1. The visual system seems to exhibit a strong tendency to normalize the range of luminance toward a canonical, 30:1, white:black range.