Balancing visual weights.

An experiment is described which is based on a peculiar response index, the visual balance, which involves the match of visual weight. The stimulus consists of a pair of grey fields, differing in their spectral reflectance factor, and the experiment is designed to determine how the balance condition depends on their relative sizes. This dependence is found to be linear when the test object is considered globally; non-linear when considering its fine intra-pair geometrical characteristics.