ON THE SATURATIONS AND CHROMATIC THRESHOLDS OF THE SPECTRAL COLOURS<sup>1</sup>

Purdy, D. M.

doi:10.1111/j.2044-8295.1931.tb00592.x

Cited by 13 publications

(21 citation statements)

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“…The approach was to assume that y1, Y2, y3 correspond respectively to perceived redness/greenness, perceived yellowness/ blueness, and perceived whiteness, and to specify non-linear colour-opponent forms forf1,f2 andf3 that would both: (i) violate Grassmanit's additivity law in eqn. (3) (the functions suggested by Jameson & Hurvich (1959), though non-linear, predict that additivity would hold) and (ii) be consistent with other linear and non-linear findings in colour perception (Purdy, 1931;Indow & Stevens, 1966;Larimer, Krantz & Cicerone, 1974, 1975Moeller, 1976). For eqn.…”

Section: Theoretical Implicationssupporting

confidence: 84%

Perception of colour in unilateral tritanopia.

Alpern¹,

Kono²,

Krantz³

1983

The Journal of Physiology

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The unilateral tritanope described in the previous paper (Alpern, Kitahara & Krantz, 1983) was able to match every narrow‐band light presented to his tritanopic eye with lights from a tristimulus colorimeter viewed in the adjacent field by the normal eye. In two regions of the spectrum (called isochromes) physically identical lights appeared identical to the observer's two eyes. One isochrome was close to ‘blue’ for the normal eye, the other was in the long‐wave spectral region seen by the normal eye predominantly as ‘red'. Between these isochromes the normal eye required less than spectral purity to match, dropping to near zero purity at 560‐570 nm. A mixture of the two isochromes that appeared purple to the normal eye appeared neutral to the tritanopic eye. Hence dichoptic matches grossly violate Grassmann's additivity law. For the normal eye colour naming conformed to typical normal results. For the tritanopic eye the results were coherent with those found by dichoptic matching: the spectrum was divided into two regions by the achromatic neutral band. To the short‐wave side, only the colour names ‘blue’ and ‘white’ were ever used. To the long‐wave side the predominant colour names were ‘red’ and ‘white’ with some ‘yellow'. Spectral lights appeared neither ‘red‐blue’ nor greenish. Surrounding the test with an annulus either 430 nm, 650 nm, or a mixture of these, fails to induce any greenish appearance, although the achromatic band shifted in the expected directions. It is concluded that there must be exactly three functionally independent, essentially non‐linear central codes for colour perception, and that these codes are different from those suggested in existing theories of colour perception.

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Section: Theoretical Implicationssupporting

confidence: 84%

Perception of colour in unilateral tritanopia.

Alpern¹,

Kono²,

Krantz³

1983

The Journal of Physiology

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“…3). The experimental data agree qualitatively with the results predicted by CA90 13,14,21,55 in the existence of a wavelength-dependent optimum luminance value. For instance, according to Purdy, 55 the optimum luminance is of about 10 td for blue, close to 40 td for red, and appears at the considerably higher level of 200 td for 565 nm.…”

Section: Discussionsupporting

confidence: 86%

“…21 Their results show the existence of a wavelength-dependent colorimetric purity value, p 0 * , for which saturation does not change with sample reflectance (which is proportional to luminance because the illumination was kept constant). Above p 0 * a reflectance value may be found yielding maximum saturation, in agreement with the results of Purdy 55 and Hunt. 13,14 For colorimetric purities below p 0 * , the saturation vs. reflectance curve has a minimum instead of a maximum.…”

Section: Discussionsupporting

confidence: 83%

On saturation and related parameters following Guth's ATD colour‐vision model

Capilla

Luque

Gómez

et al. 2001

Color Research & Application

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“…Experiments 1.5 to 1.7 concerned the construction of magnitude scales of saturation with a common unit for the four primary hues. The luminances were fixed at the following levels: R 71, Y 79, G 78, and B 65 dB re 10-10 L. According to Purdy (1931), those are approximately the levels of luminance at which the primary aperture colors give the maximum degree of saturation,…”

Section: Series 1 Saturation Of the Four Primary Huesmentioning

confidence: 99%