Abstract

We evaluated whether a self-screening hypothesis can account for changes in red–green color matches with changes in retinal illuminance and changes in the size of the matching field. The dependence of the color match on field size measured at moderate illuminances was not present at high illuminances. For color matches made with normal pupil entry, there was no need to postulate any factors other than self-screening to account for the changes with either illuminance or field size. The self-screening model allowed us to estimate the optical density of the foveal cones and the retinal illuminance that caused half of the photopigment to be bleached at equilibrium. These estimates were in quantitative agreement with previous estimates made using other techniques. We also found that the change in a color match with increasing illuminance was inconsistent with first-order kinetics.

© 1985 Optical Society of America

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  1. G. S. Wyszecki, W. S. Stiles, Color Science (Wiley, New York, 1982).
  2. In this paper we use LWS, MWS, and SWS to refer to the cones and αL, αM, and αS to refer to the extinction spectrum of the photopigments (see Appendix A).
  3. We are examining the hypothesis that for central pupil entry, with a relatively large (2.1-mm) artificial pupil, self-screening describes the effects of field size and bleaching on color matches. We are not addressing the relation between self-screening and waveguide effects that may be seen with peripheral pupil entry.
  4. W. S. Stiles, “The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new colour effect,” Proc. R. Soc. London Ser. B 123, 90–118 (1937).
    [CrossRef]
  5. J. Pokorny, V. C. Smith, “The effect of field size on red–green color mixture equations,”J. Opt. Soc. Am. 66, 705–708 (1976).
    [CrossRef] [PubMed]
  6. G. S. Brindley, “The effect on color vision of adaptation to very bright lights,”J. Physiol. 122, 332–350 (1953).
    [PubMed]
  7. G. S. Brindley, “A photochemical reaction in the human retina,” Proc. Phys. Soc. 68b, 862–870 (1955).
  8. M. Alpern, “Lack of uniformity in color matching,”J. Physiol. 288, 85–105 (1979).
  9. G. Wyszecki, W. S. Stiles, “High-level trichromatic color matching and the pigment-bleaching hypothesis,” Vision Res. 20, 23–37 (1980).
    [CrossRef] [PubMed]
  10. P. L. Walraven, M. A. Bouman, “Relation between directional sensitivity and spectral response curves in human cone vision,”J. Opt. Soc. Am. 50, 780–784 (1960).
    [CrossRef] [PubMed]
  11. J. Pokorny, V. C. Smith, G. Verriest, A. J. L. Pinckers, Congenital and Acquired Color Vision Defects (Grune and Stratton, New York, 1979).
  12. For example, S. L. Polyak, The Retina (U. Chicago Press, Chicago, Ill., 1941).
  13. A 2.1-mm aperture permits both high retinal illuminances and homogeneous appearing matching fields. We monitored the size and the position of the pupils of all except four of the observers using an infrared TV system. The natural pupil was never smaller than 2.1 mm, even at the highest illuminances.
  14. This configuration allowed us to use a fixed standard and thus to specify uniquely the retinal illuminance.
  15. The log(R/G) ratio values are expressed in terms of the photocell’s “ photopic ” spectral sensitivity.
  16. To determine whether the 480-nm desaturant had any effect on the R/G ratio, observer SB performed complete trichromatic matches of the 589.6-nm standard plus a 480-nm primary to the mixture of the 650- and 546-nm primaries. When the log(R/G) ratios from the control experiment were compared with data from the main experiment, we found no reliable difference in the measured R/G ratios. We also made a series of dichromatic matches, varying the relative amount of the whole-field 480-nm desaturant. There was no reliable effect of the 480-nm desaturant on log(R/G).
  17. To determine the appropriate adaptation period we performed control experiments in which the color match was measured as a function of time following exposure to each retinal illuminance. For all illuminances except 11,200 Td the bleaching-induced shift in the color match was complete within 3 min. At 11,200 Td there was a very slow bleaching effect that could take up to 15 min to reach asymptote. However, the total error that this slow shift could account for is of the order of 0.02 log unit. The 10-deg matches were made to ensure an adaptation period at each retinal illuminance. Data obtained at this field size were not recorded.
  18. The first author made matches up to 600,000 Td with no evidence of further changes in the color match beyond those evident at 90,000 Td.
  19. V. C. Smith, J. Pokorny, S. S. Starr, “Variability of color matching data. I. Interobserver variability in the unit coordinates,” Vision Res. 16, 1087–1094 (1976).
    [CrossRef]
  20. There is an arbitrary vertical normalization of the theoretical curves to bring them into alignment with the calibrated log(R/G) values. This normalization does not affect the shape of the functions.
  21. See also B. R. Wooten, K. Fuld, M. Moore, L. Katz, “The Stiles–Crawford II effect at high bleaching levels,” in Visual Psychophysics and Physiology, J. Armington, J. Krauskopf, B. R. Wooten, eds. (Academic, New York, 1978).
    [CrossRef]
  22. J. K. Bowmaker, H. J. A. Dartnall, “Visual pigments of rods and cones in a human retina,”J. Physiol. 298, 501–511 (1980).
    [PubMed]
  23. V. C. Smith, J. Pokorny, “Psychophysical estimates of optical density in human cones,” Vision Res. 13, 1199–1202 (1973).
    [CrossRef] [PubMed]
  24. S. S. Miller, “Psychophysical estimates of visual pigment densities in red–green dichromats,”J. Physiol. 223, 89–107 (1972).
    [PubMed]
  25. Wooten21 and Fuld et al. [K. Fuld, B. R. Wooten, L. Katz, “The Stiles–Crawford hue shift following photopigment depletion,” Nature 279, 152–154, 1979)] have argued that self-screening cannot account for the total change in the color match at high illuminance. Their argument is based on the failure of the color-match data to fall on a straight line when plotted against percent pigment bleached as computed from first-order kinetics.
    [CrossRef] [PubMed]
  26. Rms errors were between 0.001 and 0.052.
  27. There were no reliable evidence of a systematic effect of field size on the half-bleach illuminance for our six observers. The two observers with the largest effects were our most variable observers and have the lowest reliability in the estimate of their half-bleach illuminance.
  28. P. E. King-Smith, “The optical density of erythrolabe determined by a new method,”J. Physiol. 230, 551–560 (1973).
    [PubMed]
  29. This correlation (although statistically significant) is not stressed since if the two extreme points are omitted the correlation coefficient drops to 0. 2.
  30. W. A. H. Rushton, G. H. Henry, “Bleaching and regeneration of cone pigments in man,” Vision Res. 8, 617–631 (1968).
    [CrossRef] [PubMed]
  31. M. Hollins, M. Alpern, “Dark adaptation and visual pigment regeneration in human cones,”J. Gen. Physiol. 62, 430–447 (1973).
    [CrossRef] [PubMed]
  32. S. K. Shevell, “Saturation in human cones,” Vision Res. 17, 427–434 (1977).
    [CrossRef] [PubMed]
  33. We have normalized these curves at the half-bleach illuminance value. That is, we assumed that our estimate of the half-bleach illuminance was accurate and then used that estimate as a parameter for the first order prediction. This assumption does not affect the difference in shape between the data and the theoretical prediction. We show the data of only one observer, although similar deviations from the first-order predictions are evident for all observers. In addition, the data of Wyszecki34 and Alpern8 also show the same trend. Wyszecki and Stiles9 have shown that complete sets of color-matching functions obtained at high illuminances are compatible with the self-screening hypothesis.
  34. G. Wyszecki, “Color matching at moderate to high levels of retinal illuminance, a pilot study,” Vision Res. 18, 341–346 (1978).
    [CrossRef]
  35. V. C. Smith, J. Pokorny, D. V. Norren, “Densitometric measurements of human cone photopigment kinetics,” Vision Res. 23, 517–524 (1983).
    [CrossRef]
  36. H. Ripps, L. Mehaffey, I. M. Sigel, “Rhodopsin kinetics in the cat retina,”J. Gen. Physiol. 77, 317–334 (1981).
    [CrossRef] [PubMed]
  37. Extinction spectra were computed from the fundamentals of Smith et al.19 by using the authors’ specified optical densities. As stated by the authors, the extinction spectra are well fitted by the iodopsin nomogram.
  38. G. L. Howett, “Variation of absorptance-curve shape with changes in pigment concentration,”J. Res. Nat. Bur. Stand. Sect. A 72, 309–340 (1968).
    [CrossRef]

1983 (1)

V. C. Smith, J. Pokorny, D. V. Norren, “Densitometric measurements of human cone photopigment kinetics,” Vision Res. 23, 517–524 (1983).
[CrossRef]

1981 (1)

H. Ripps, L. Mehaffey, I. M. Sigel, “Rhodopsin kinetics in the cat retina,”J. Gen. Physiol. 77, 317–334 (1981).
[CrossRef] [PubMed]

1980 (2)

G. Wyszecki, W. S. Stiles, “High-level trichromatic color matching and the pigment-bleaching hypothesis,” Vision Res. 20, 23–37 (1980).
[CrossRef] [PubMed]

J. K. Bowmaker, H. J. A. Dartnall, “Visual pigments of rods and cones in a human retina,”J. Physiol. 298, 501–511 (1980).
[PubMed]

1979 (2)

Wooten21 and Fuld et al. [K. Fuld, B. R. Wooten, L. Katz, “The Stiles–Crawford hue shift following photopigment depletion,” Nature 279, 152–154, 1979)] have argued that self-screening cannot account for the total change in the color match at high illuminance. Their argument is based on the failure of the color-match data to fall on a straight line when plotted against percent pigment bleached as computed from first-order kinetics.
[CrossRef] [PubMed]

M. Alpern, “Lack of uniformity in color matching,”J. Physiol. 288, 85–105 (1979).

1978 (1)

G. Wyszecki, “Color matching at moderate to high levels of retinal illuminance, a pilot study,” Vision Res. 18, 341–346 (1978).
[CrossRef]

1977 (1)

S. K. Shevell, “Saturation in human cones,” Vision Res. 17, 427–434 (1977).
[CrossRef] [PubMed]

1976 (2)

V. C. Smith, J. Pokorny, S. S. Starr, “Variability of color matching data. I. Interobserver variability in the unit coordinates,” Vision Res. 16, 1087–1094 (1976).
[CrossRef]

J. Pokorny, V. C. Smith, “The effect of field size on red–green color mixture equations,”J. Opt. Soc. Am. 66, 705–708 (1976).
[CrossRef] [PubMed]

1973 (3)

M. Hollins, M. Alpern, “Dark adaptation and visual pigment regeneration in human cones,”J. Gen. Physiol. 62, 430–447 (1973).
[CrossRef] [PubMed]

P. E. King-Smith, “The optical density of erythrolabe determined by a new method,”J. Physiol. 230, 551–560 (1973).
[PubMed]

V. C. Smith, J. Pokorny, “Psychophysical estimates of optical density in human cones,” Vision Res. 13, 1199–1202 (1973).
[CrossRef] [PubMed]

1972 (1)

S. S. Miller, “Psychophysical estimates of visual pigment densities in red–green dichromats,”J. Physiol. 223, 89–107 (1972).
[PubMed]

1968 (2)

W. A. H. Rushton, G. H. Henry, “Bleaching and regeneration of cone pigments in man,” Vision Res. 8, 617–631 (1968).
[CrossRef] [PubMed]

G. L. Howett, “Variation of absorptance-curve shape with changes in pigment concentration,”J. Res. Nat. Bur. Stand. Sect. A 72, 309–340 (1968).
[CrossRef]

1960 (1)

1955 (1)

G. S. Brindley, “A photochemical reaction in the human retina,” Proc. Phys. Soc. 68b, 862–870 (1955).

1953 (1)

G. S. Brindley, “The effect on color vision of adaptation to very bright lights,”J. Physiol. 122, 332–350 (1953).
[PubMed]

1937 (1)

W. S. Stiles, “The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new colour effect,” Proc. R. Soc. London Ser. B 123, 90–118 (1937).
[CrossRef]

Alpern, M.

M. Alpern, “Lack of uniformity in color matching,”J. Physiol. 288, 85–105 (1979).

M. Hollins, M. Alpern, “Dark adaptation and visual pigment regeneration in human cones,”J. Gen. Physiol. 62, 430–447 (1973).
[CrossRef] [PubMed]

Bouman, M. A.

Bowmaker, J. K.

J. K. Bowmaker, H. J. A. Dartnall, “Visual pigments of rods and cones in a human retina,”J. Physiol. 298, 501–511 (1980).
[PubMed]

Brindley, G. S.

G. S. Brindley, “A photochemical reaction in the human retina,” Proc. Phys. Soc. 68b, 862–870 (1955).

G. S. Brindley, “The effect on color vision of adaptation to very bright lights,”J. Physiol. 122, 332–350 (1953).
[PubMed]

Dartnall, H. J. A.

J. K. Bowmaker, H. J. A. Dartnall, “Visual pigments of rods and cones in a human retina,”J. Physiol. 298, 501–511 (1980).
[PubMed]

Fuld, K.

Wooten21 and Fuld et al. [K. Fuld, B. R. Wooten, L. Katz, “The Stiles–Crawford hue shift following photopigment depletion,” Nature 279, 152–154, 1979)] have argued that self-screening cannot account for the total change in the color match at high illuminance. Their argument is based on the failure of the color-match data to fall on a straight line when plotted against percent pigment bleached as computed from first-order kinetics.
[CrossRef] [PubMed]

See also B. R. Wooten, K. Fuld, M. Moore, L. Katz, “The Stiles–Crawford II effect at high bleaching levels,” in Visual Psychophysics and Physiology, J. Armington, J. Krauskopf, B. R. Wooten, eds. (Academic, New York, 1978).
[CrossRef]

Henry, G. H.

W. A. H. Rushton, G. H. Henry, “Bleaching and regeneration of cone pigments in man,” Vision Res. 8, 617–631 (1968).
[CrossRef] [PubMed]

Hollins, M.

M. Hollins, M. Alpern, “Dark adaptation and visual pigment regeneration in human cones,”J. Gen. Physiol. 62, 430–447 (1973).
[CrossRef] [PubMed]

Howett, G. L.

G. L. Howett, “Variation of absorptance-curve shape with changes in pigment concentration,”J. Res. Nat. Bur. Stand. Sect. A 72, 309–340 (1968).
[CrossRef]

Katz, L.

Wooten21 and Fuld et al. [K. Fuld, B. R. Wooten, L. Katz, “The Stiles–Crawford hue shift following photopigment depletion,” Nature 279, 152–154, 1979)] have argued that self-screening cannot account for the total change in the color match at high illuminance. Their argument is based on the failure of the color-match data to fall on a straight line when plotted against percent pigment bleached as computed from first-order kinetics.
[CrossRef] [PubMed]

See also B. R. Wooten, K. Fuld, M. Moore, L. Katz, “The Stiles–Crawford II effect at high bleaching levels,” in Visual Psychophysics and Physiology, J. Armington, J. Krauskopf, B. R. Wooten, eds. (Academic, New York, 1978).
[CrossRef]

King-Smith, P. E.

P. E. King-Smith, “The optical density of erythrolabe determined by a new method,”J. Physiol. 230, 551–560 (1973).
[PubMed]

Mehaffey, L.

H. Ripps, L. Mehaffey, I. M. Sigel, “Rhodopsin kinetics in the cat retina,”J. Gen. Physiol. 77, 317–334 (1981).
[CrossRef] [PubMed]

Miller, S. S.

S. S. Miller, “Psychophysical estimates of visual pigment densities in red–green dichromats,”J. Physiol. 223, 89–107 (1972).
[PubMed]

Moore, M.

See also B. R. Wooten, K. Fuld, M. Moore, L. Katz, “The Stiles–Crawford II effect at high bleaching levels,” in Visual Psychophysics and Physiology, J. Armington, J. Krauskopf, B. R. Wooten, eds. (Academic, New York, 1978).
[CrossRef]

Norren, D. V.

V. C. Smith, J. Pokorny, D. V. Norren, “Densitometric measurements of human cone photopigment kinetics,” Vision Res. 23, 517–524 (1983).
[CrossRef]

Pinckers, A. J. L.

J. Pokorny, V. C. Smith, G. Verriest, A. J. L. Pinckers, Congenital and Acquired Color Vision Defects (Grune and Stratton, New York, 1979).

Pokorny, J.

V. C. Smith, J. Pokorny, D. V. Norren, “Densitometric measurements of human cone photopigment kinetics,” Vision Res. 23, 517–524 (1983).
[CrossRef]

V. C. Smith, J. Pokorny, S. S. Starr, “Variability of color matching data. I. Interobserver variability in the unit coordinates,” Vision Res. 16, 1087–1094 (1976).
[CrossRef]

J. Pokorny, V. C. Smith, “The effect of field size on red–green color mixture equations,”J. Opt. Soc. Am. 66, 705–708 (1976).
[CrossRef] [PubMed]

V. C. Smith, J. Pokorny, “Psychophysical estimates of optical density in human cones,” Vision Res. 13, 1199–1202 (1973).
[CrossRef] [PubMed]

J. Pokorny, V. C. Smith, G. Verriest, A. J. L. Pinckers, Congenital and Acquired Color Vision Defects (Grune and Stratton, New York, 1979).

Polyak, S. L.

For example, S. L. Polyak, The Retina (U. Chicago Press, Chicago, Ill., 1941).

Ripps, H.

H. Ripps, L. Mehaffey, I. M. Sigel, “Rhodopsin kinetics in the cat retina,”J. Gen. Physiol. 77, 317–334 (1981).
[CrossRef] [PubMed]

Rushton, W. A. H.

W. A. H. Rushton, G. H. Henry, “Bleaching and regeneration of cone pigments in man,” Vision Res. 8, 617–631 (1968).
[CrossRef] [PubMed]

Shevell, S. K.

S. K. Shevell, “Saturation in human cones,” Vision Res. 17, 427–434 (1977).
[CrossRef] [PubMed]

Sigel, I. M.

H. Ripps, L. Mehaffey, I. M. Sigel, “Rhodopsin kinetics in the cat retina,”J. Gen. Physiol. 77, 317–334 (1981).
[CrossRef] [PubMed]

Smith, V. C.

V. C. Smith, J. Pokorny, D. V. Norren, “Densitometric measurements of human cone photopigment kinetics,” Vision Res. 23, 517–524 (1983).
[CrossRef]

V. C. Smith, J. Pokorny, S. S. Starr, “Variability of color matching data. I. Interobserver variability in the unit coordinates,” Vision Res. 16, 1087–1094 (1976).
[CrossRef]

J. Pokorny, V. C. Smith, “The effect of field size on red–green color mixture equations,”J. Opt. Soc. Am. 66, 705–708 (1976).
[CrossRef] [PubMed]

V. C. Smith, J. Pokorny, “Psychophysical estimates of optical density in human cones,” Vision Res. 13, 1199–1202 (1973).
[CrossRef] [PubMed]

J. Pokorny, V. C. Smith, G. Verriest, A. J. L. Pinckers, Congenital and Acquired Color Vision Defects (Grune and Stratton, New York, 1979).

Starr, S. S.

V. C. Smith, J. Pokorny, S. S. Starr, “Variability of color matching data. I. Interobserver variability in the unit coordinates,” Vision Res. 16, 1087–1094 (1976).
[CrossRef]

Stiles, W. S.

G. Wyszecki, W. S. Stiles, “High-level trichromatic color matching and the pigment-bleaching hypothesis,” Vision Res. 20, 23–37 (1980).
[CrossRef] [PubMed]

W. S. Stiles, “The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new colour effect,” Proc. R. Soc. London Ser. B 123, 90–118 (1937).
[CrossRef]

G. S. Wyszecki, W. S. Stiles, Color Science (Wiley, New York, 1982).

Verriest, G.

J. Pokorny, V. C. Smith, G. Verriest, A. J. L. Pinckers, Congenital and Acquired Color Vision Defects (Grune and Stratton, New York, 1979).

Walraven, P. L.

Wooten, B. R.

Wooten21 and Fuld et al. [K. Fuld, B. R. Wooten, L. Katz, “The Stiles–Crawford hue shift following photopigment depletion,” Nature 279, 152–154, 1979)] have argued that self-screening cannot account for the total change in the color match at high illuminance. Their argument is based on the failure of the color-match data to fall on a straight line when plotted against percent pigment bleached as computed from first-order kinetics.
[CrossRef] [PubMed]

See also B. R. Wooten, K. Fuld, M. Moore, L. Katz, “The Stiles–Crawford II effect at high bleaching levels,” in Visual Psychophysics and Physiology, J. Armington, J. Krauskopf, B. R. Wooten, eds. (Academic, New York, 1978).
[CrossRef]

Wyszecki, G.

G. Wyszecki, W. S. Stiles, “High-level trichromatic color matching and the pigment-bleaching hypothesis,” Vision Res. 20, 23–37 (1980).
[CrossRef] [PubMed]

G. Wyszecki, “Color matching at moderate to high levels of retinal illuminance, a pilot study,” Vision Res. 18, 341–346 (1978).
[CrossRef]

Wyszecki, G. S.

G. S. Wyszecki, W. S. Stiles, Color Science (Wiley, New York, 1982).

J. Gen. Physiol. (2)

M. Hollins, M. Alpern, “Dark adaptation and visual pigment regeneration in human cones,”J. Gen. Physiol. 62, 430–447 (1973).
[CrossRef] [PubMed]

H. Ripps, L. Mehaffey, I. M. Sigel, “Rhodopsin kinetics in the cat retina,”J. Gen. Physiol. 77, 317–334 (1981).
[CrossRef] [PubMed]

J. Opt. Soc. Am. (2)

J. Physiol. (5)

M. Alpern, “Lack of uniformity in color matching,”J. Physiol. 288, 85–105 (1979).

P. E. King-Smith, “The optical density of erythrolabe determined by a new method,”J. Physiol. 230, 551–560 (1973).
[PubMed]

G. S. Brindley, “The effect on color vision of adaptation to very bright lights,”J. Physiol. 122, 332–350 (1953).
[PubMed]

J. K. Bowmaker, H. J. A. Dartnall, “Visual pigments of rods and cones in a human retina,”J. Physiol. 298, 501–511 (1980).
[PubMed]

S. S. Miller, “Psychophysical estimates of visual pigment densities in red–green dichromats,”J. Physiol. 223, 89–107 (1972).
[PubMed]

J. Res. Nat. Bur. Stand. Sect. A (1)

G. L. Howett, “Variation of absorptance-curve shape with changes in pigment concentration,”J. Res. Nat. Bur. Stand. Sect. A 72, 309–340 (1968).
[CrossRef]

Nature (1)

Wooten21 and Fuld et al. [K. Fuld, B. R. Wooten, L. Katz, “The Stiles–Crawford hue shift following photopigment depletion,” Nature 279, 152–154, 1979)] have argued that self-screening cannot account for the total change in the color match at high illuminance. Their argument is based on the failure of the color-match data to fall on a straight line when plotted against percent pigment bleached as computed from first-order kinetics.
[CrossRef] [PubMed]

Proc. Phys. Soc. (1)

G. S. Brindley, “A photochemical reaction in the human retina,” Proc. Phys. Soc. 68b, 862–870 (1955).

Proc. R. Soc. London Ser. B (1)

W. S. Stiles, “The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new colour effect,” Proc. R. Soc. London Ser. B 123, 90–118 (1937).
[CrossRef]

Vision Res. (7)

W. A. H. Rushton, G. H. Henry, “Bleaching and regeneration of cone pigments in man,” Vision Res. 8, 617–631 (1968).
[CrossRef] [PubMed]

S. K. Shevell, “Saturation in human cones,” Vision Res. 17, 427–434 (1977).
[CrossRef] [PubMed]

G. Wyszecki, “Color matching at moderate to high levels of retinal illuminance, a pilot study,” Vision Res. 18, 341–346 (1978).
[CrossRef]

V. C. Smith, J. Pokorny, D. V. Norren, “Densitometric measurements of human cone photopigment kinetics,” Vision Res. 23, 517–524 (1983).
[CrossRef]

V. C. Smith, J. Pokorny, “Psychophysical estimates of optical density in human cones,” Vision Res. 13, 1199–1202 (1973).
[CrossRef] [PubMed]

V. C. Smith, J. Pokorny, S. S. Starr, “Variability of color matching data. I. Interobserver variability in the unit coordinates,” Vision Res. 16, 1087–1094 (1976).
[CrossRef]

G. Wyszecki, W. S. Stiles, “High-level trichromatic color matching and the pigment-bleaching hypothesis,” Vision Res. 20, 23–37 (1980).
[CrossRef] [PubMed]

Other (18)

There is an arbitrary vertical normalization of the theoretical curves to bring them into alignment with the calibrated log(R/G) values. This normalization does not affect the shape of the functions.

See also B. R. Wooten, K. Fuld, M. Moore, L. Katz, “The Stiles–Crawford II effect at high bleaching levels,” in Visual Psychophysics and Physiology, J. Armington, J. Krauskopf, B. R. Wooten, eds. (Academic, New York, 1978).
[CrossRef]

Rms errors were between 0.001 and 0.052.

There were no reliable evidence of a systematic effect of field size on the half-bleach illuminance for our six observers. The two observers with the largest effects were our most variable observers and have the lowest reliability in the estimate of their half-bleach illuminance.

J. Pokorny, V. C. Smith, G. Verriest, A. J. L. Pinckers, Congenital and Acquired Color Vision Defects (Grune and Stratton, New York, 1979).

For example, S. L. Polyak, The Retina (U. Chicago Press, Chicago, Ill., 1941).

A 2.1-mm aperture permits both high retinal illuminances and homogeneous appearing matching fields. We monitored the size and the position of the pupils of all except four of the observers using an infrared TV system. The natural pupil was never smaller than 2.1 mm, even at the highest illuminances.

This configuration allowed us to use a fixed standard and thus to specify uniquely the retinal illuminance.

The log(R/G) ratio values are expressed in terms of the photocell’s “ photopic ” spectral sensitivity.

To determine whether the 480-nm desaturant had any effect on the R/G ratio, observer SB performed complete trichromatic matches of the 589.6-nm standard plus a 480-nm primary to the mixture of the 650- and 546-nm primaries. When the log(R/G) ratios from the control experiment were compared with data from the main experiment, we found no reliable difference in the measured R/G ratios. We also made a series of dichromatic matches, varying the relative amount of the whole-field 480-nm desaturant. There was no reliable effect of the 480-nm desaturant on log(R/G).

To determine the appropriate adaptation period we performed control experiments in which the color match was measured as a function of time following exposure to each retinal illuminance. For all illuminances except 11,200 Td the bleaching-induced shift in the color match was complete within 3 min. At 11,200 Td there was a very slow bleaching effect that could take up to 15 min to reach asymptote. However, the total error that this slow shift could account for is of the order of 0.02 log unit. The 10-deg matches were made to ensure an adaptation period at each retinal illuminance. Data obtained at this field size were not recorded.

The first author made matches up to 600,000 Td with no evidence of further changes in the color match beyond those evident at 90,000 Td.

Extinction spectra were computed from the fundamentals of Smith et al.19 by using the authors’ specified optical densities. As stated by the authors, the extinction spectra are well fitted by the iodopsin nomogram.

We have normalized these curves at the half-bleach illuminance value. That is, we assumed that our estimate of the half-bleach illuminance was accurate and then used that estimate as a parameter for the first order prediction. This assumption does not affect the difference in shape between the data and the theoretical prediction. We show the data of only one observer, although similar deviations from the first-order predictions are evident for all observers. In addition, the data of Wyszecki34 and Alpern8 also show the same trend. Wyszecki and Stiles9 have shown that complete sets of color-matching functions obtained at high illuminances are compatible with the self-screening hypothesis.

This correlation (although statistically significant) is not stressed since if the two extreme points are omitted the correlation coefficient drops to 0. 2.

G. S. Wyszecki, W. S. Stiles, Color Science (Wiley, New York, 1982).

In this paper we use LWS, MWS, and SWS to refer to the cones and αL, αM, and αS to refer to the extinction spectrum of the photopigments (see Appendix A).

We are examining the hypothesis that for central pupil entry, with a relatively large (2.1-mm) artificial pupil, self-screening describes the effects of field size and bleaching on color matches. We are not addressing the relation between self-screening and waveguide effects that may be seen with peripheral pupil entry.

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Figures (7)

Fig. 1
Fig. 1

Color-matching data for observer AE at four field sizes: 1 deg (hexagons), 2 deg (circles), 4 deg (squares), and 8 deg (triangles). The log(R/G) ratio is the log of the ratio of the amounts of the 650- and 546-nm primaries required to match a 589.6-nm standard.

Fig. 2
Fig. 2

Average color-match data for six observers at three field sizes. Symbols as in Fig. 1.

Fig. 3
Fig. 3

Color-matching data for individual observers at the 4-deg field size.

Fig. 4
Fig. 4

Effect of optical density on log(R/G). The log(R/G) values are predicted from Beer’s law (see Appendix A). The two curves represent different ratios of the densities of photopigment in the LWS and MWS cones. The solid line is based on equal densities in the two cones; the dashed lines show the prediction if the LWS density is 1.5 times the MWS density.

Fig. 5
Fig. 5

Computed optical densities for all observers at all field sizes. Points from the same observer are connected by solid lines. These values were computed assuming that the peak optical densities of the LWS and MWS cones were equal. If it were assumed that the LWS cone density were 1.3 times that of the MWS cone, the optical densities would be scaled by a factor of 1.2 (see Fig. 4).

Fig. 6
Fig. 6

Comparison of the half-bleach illuminance (I0) values as a function of optical density for all observers at 4 deg.

Fig. 7
Fig. 7

Comparison of the observed dependence of the color match on retinal illuminance (solid line) with the predictions of the first-order kinetic equation (dashed line) for one observer. Results are similar for all observers.33

Equations (7)

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λ L ( λ ) Q 1 ( λ ) d λ = λ L ( λ ) Q 2 ( λ ) d λ ,
λ M ( λ ) Q 1 ( λ ) d λ = λ M ( λ ) Q 2 ( λ ) d λ ,
λ S ( λ ) Q 1 ( λ ) d λ = λ S ( λ ) Q 2 ( λ ) d λ .
F ( λ ) = 1 - exp [ - α ( λ ) c l ] ,
Q ( 590 ) L ( 590 ) = Q ( 546 ) L ( 546 ) + Q ( 650 ) L ( 650 )
Q ( 590 ) M ( 590 ) = Q ( 546 ) M ( 546 ) + Q ( 650 ) M ( 650 ) ,
{ 1 - exp [ - α L ( 590 ) c L l L ( f L ) ] } { 1 - exp [ - α M ( 590 ) c M l M ( f M ) ] } = X { 1 - exp [ - α L ( 546 ) c L l L ( f L ) ] } + { 1 - exp [ - α L ( 650 ) c L l L ( f L ) ] } X { 1 - exp [ - α M ( 546 ) c M l M ( f M ) ] } + { 1 - exp [ - α M ( 650 ) c M l M ( f M ) ] }

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