2004 Volume 28 Issue 1 Pages 50-57
Understanding illumination is necessary for the perception of color and brightness in an object’s surface. We call such understanding the recognized visual space of illumination, or RVSI. In particular, we use the term ‘brightness size’ of RVSI to describe an observer’s perception about the intensity of illumination. The brightness size of RVSI is evaluated using the border luminance between surface color and unnatural surface color modes. We established a new estimation method of space brightness in natural environments and investigated what determines the brightness size of RVSI. We measured the border luminance of the test patch (N5 gray, mat) to test three candidates for determining the size: illuminance (1), spatially averaged luminance across a visual field (2), and highest luminance (3). The border luminance was proportional to the illuminance and was almost equal to the luminance of the object with the highest lightness. However, there was no effect from the luminance of the object with the light-source color mode, regardless of its luminance. The effect from the averaged luminance was not significant. We concluded the illuminance to be a major determinant of the brightness size of RVSI.
