Procedures for Testing Color Vision Report of Working Group 41 (1981) / Chapter Skim
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Appendix: Understanding Test Design
Appendix: Understanding Test Design
Pages 97-110
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From page 97... ...
An isosceles triangle completely encloses the experimentally determined chromaticity diagram. The spectral wavelengths are represented around the perimeter of the chromaticity diagram, which is called the spectrum locus, and equal energy Awaited occurs in the center.
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From page 98... ...
is not specified by the chromaticity chart, but in general it can be said that saturation along any line from the center to the spectrum locus increases with the distance from the center. The line connecting the coordinates for 380 nm and 700 nm is identified as the line of nonspectral purples.
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From page 99... ...
The CIE standard observer represents a person with average visual photopigments, lens, and macular pigment absorptions. The isochromatic lines are thus similarly indicative of those expected for an average group of dichromats whose ocular media have characteristics similar to those of normal trichromats.
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From page 100... ...
. O 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 O.9 1.0 1.1 1.2 1.3 1.4 X FIGURE A-2 Confusion lines for protanopes (upper panel)
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From page 101... ...
This principle is illustrated in Figure A-3 with reference to the screening and quantitative red-green plates of the Tokyo Medical College. However, the ability of a given color-defective observer to read a set of plates depends not only on the observer's chromatic discriminative ability but also on how appropriate the selected confusion colors are for that observer.
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From page 102... ...
For example, on plate 5 of the Ishihara test (5th edition) , the normal observer sees a .5" composed of yellow-green and light green dots on a background of light and dark orange and pink dots, whereas the red-green dichromat reports seeing a rather neutral .2.
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From page 103... ...
For a normal observer, whose reference point for color is the position of Illuminant C, two of the clusters constitute the green figure and two constitute the orange background. The confusion lines for red-green dichromats, however, indicate that their reference point for color appears to be in the red-purple areas of the chromaticity diagram.
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From page 104... ...
The latter perceive two color groupings that are distinct enough from each other to follow two separate i~ochromatic lines: the more saturated orange, khaki, and yellow-green dots form the background, and the less saturated pinks, grays, and greens form the figure. Figure A-6 shows the loci for colors used in plates ,0 and 11 of the Ishihara plates (Sth edition)
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From page 105... ...
Since the confusion lines connect pairs of cape that are identical or closely similar for a given dichromat, the expectation in that the protanope or deuteranope will make a characteristic arrangement of caps, connecting caps that oppose each other in the color circle but that lie on the appropriate confusion line. For protanopes a possible arrangement is: P 15, 1, 14, 2, 13, 3, 12, 4, 11, 5, 10, 6, 9, 7, 8.
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From page 106... ...
-15 Test. Confusion lines are indicated by dashed lines for protanopes {upper panel)
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From page 107... ...
is usually called an anomaloscope, that is, an instrument for specifying anomalous color vision. Today the anomaloscope is used as an instrument capable of measur ing var iations in color vision for normal, anomalous, and dichromatic observers, not only in the classic Rayleigh equation but also in other combinations of two lights to match a third.
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From page 108... ...
Thus in the Nagel Model II, the mixture field originally consisted of a red stimulus wavelength 671 nm [lithium line) , and a green stimulus of t
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From page 109... ...
Because desaturation was not available on the Nagel Model II, the Engelking-Trendelenburg equation is rarely used. The luminance of mixtures of primaries, especially at the most frequently chosen ratio, must be well above the threshold level for cone vision but preferably at the top of the mesopic range of vision, although the critical luminance will depend primarily on the size of the viewing aperture.
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From page 110... ...
0.8 0 7 0 6 0.4 03 02 01 o O 1 -02 110 = , , , 520 ~530 510 ~ \~550 500 ~ 70 N - 490~ 470\ _ _ -0.3 -0.4 ~~o~ 1 . · , ~ I I I I · I · · ~ ~ 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 13 14 X FIGURE A-9 Chromaticities for primaries and test colors on the Nagel Model I and the Pickford-Nicolson anomaloscopes.
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