Abstract

A new heterochromatic photometer has been devised that combines the features of the direct-comparison and the flicker methods. Two contiguous photometric fields (for example, red and blue) are viewed in a plane mirror which is pivoted at one end and oscillates approximately 2° at a frequency of 5 to 40 cps. Each left or right movement of the mirror is of constant velocity. This mirror oscillation causes the image of the vertical boundary between the two fields to oscillate and blur into a central zone in which the two colors are mixed. The mixed zone has a color graduation with the colors at its two boundaries the same as the adjacent fields, and a photometric match is achieved when the luminance becomes uniform and both boundary lines disappear. The disappearance of both boundary lines has proved to be a more precise indication than the disappearance of flicker in the central zone. Various tests, using both experienced and inexperienced observers, showed that in both ease of use and precision the new method is superior to the direct-comparison and the flicker methods. These tests involved field luminances from 32.50 candles/ft² to 0.0011 candles/ft².

© 1961 Optical Society of America

Minimally Distinct Border as a Preferred Psychophysical Criterion in Visual Heterochromatic Photometry*

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Comparison of Four Methods of Heterochromatic Photometry

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