Abstract

Lowry’s results (1931) for brightness discrimination have been confirmed, his conclusion extended, and his recommendation amplified. The results of the present experiment, for example, show clearly that the root-mean-square departure σΔI is directly proportional to ΔI. (This is here called Crozier’s law.) Moreover, since ΔI is known to vary inversely with the size of the retinal field, the use of a test field which produces a large retinal area (central fixation) is to be recommended for increased precision in photometric work.

© 1937 Optical Society of America

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