Abstract
THE interesting visual phenomenon described by Mr. Dartnall in NATURE recently1 was observed by Helmholtz many years ago2. The effect—the appearance of a purple after-image in a patch of light alternating at a frequency just below the critical frequency—no doubt arises from the differential rate of development of after-images of different colour, but some observers whom I tested a year or two ago were unable to see the phenomenon, at least under conditions when it could be readily observed by myself and others. I then found that those who could not see the effect were those who gave a delayed type of recovery curve after light-adaptation3 as recorded by the binocular matching method.
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NATURE, 142, 1000 (1938).
v. Helmholtz, H., "Physiological Optics", 2, 255 (Edn. by Optical Society of America, 1924).
Wright, W. D., "Perception of Light" (Blackie and Son, 1938).
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WRIGHT, W. A Visual Phenomenon. Nature 142, 1163 (1938). https://doi.org/10.1038/1421163b0
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DOI: https://doi.org/10.1038/1421163b0
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