L. C. Thomson and W. D. Wright, J. Physiol. (London) 105, 316 (1947).
W. D. Wright and F. H. G. Pitt, Proc. Phys. Soc. (London) 46, 459 (1934).
R. E. Bedford and G. W. Wyszecki, J. Opt. Soc. Am. 48, 129 (1958).
The data presented in Figs. 2–5 required between five and ten sessions for each added-field luminance. The task is difficult and there is considerable variability both within and between subjects. We consider that the functions indicate definite trends. Data from other subjects indicate that the added-field luminances required to produce a given effect (e.g., loss of discrimination above 520 nm with added red) are of similar magnitude to those for JS.
It might be questioned whether the relative symmetry of the functions obtained with a 435-nm added field reflects the fact that we have treated the data in terms of wavelength rather than frequency. There have been numerous suggestions that a frequency rather than a wavelength scale is the appropriate metric for treating visual functions. J. P. Heilman [J. Opt. Soc. Am. 57,281 (1967)] has noted that the conversion is nonlinear for the ordinate as well as the abscissa when wavelength-discrimination data are plotted. Even with this conversion, with a red added field, the loss of discrimination in the red is very rapid compared with the loss in the blue. The blue added-field data show greater symmetry when expressed in frequency units; however, the differential effects of the 650- and 435-nm added fields are still apparent.
W. D. Wright, J. Physiol. (London) 87, 23 (1936); J. Cohen, Am J. Psychol. 59, 84 (1946); G. S. Brindley, J. Physiol (London) 122, 332 (1953).
W. F. Hamilton and H. Laurens, Am. J. Physiol. 65, 569 (1923); W. D. Wright, Researches on Normal and Defective Color Vision (H. Kimpton, London, C. V. Mosby, St. Louis, 1946), p. 203.
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R. M. Boynton, G. Kandel, and J. W. Onley, J. Opt. Soc. Am. 49, 654 (1959).
A protanope showed a similar displacement of his minimum toward shorter wavelengths with a high-luminance red added field.