In this experiment, observers estimated the perceived brightness of a central and surrounding area under varying luminances, luminance ratios, and central area sizes by using a 13-step scale in a lighting condition with two different luminance areas.1. Perceived brightness in the surrounding area was darker than usual in the high central luminance condition.2. Perceived brightness in the surrounding area was different from that in the central area and changed independently.3. Perceived brightness had a linear relation to the luminance logarithm in two areas, consistent with Weber amp; Fechner's logarithmic law. In addition, the linear regressions' coefficients changed depending on the contrasts (luminance ratio) and central area sizes.
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