Figure 1.
CIE 1931 chromaticity diagrams showing confusion loci for illuminant C with main confusion locus in heavy black line.
A. For protanopia. Neutral point and confusion point P are labeled. B. For deuteranopia. Confusion point D is labeled. Redrawn from Judd [25].
Figure 2.
As for Figure 1 but for tritanopia (black lines).
Main confusion loci from Figures A (red line) and B (green line) are superimposed. Redrawn from Judd [25].
Table 1.
Characteristics of dichromacy showing wavelengths nm of neutral points and confusion points for indicated illuminant CCT, hue names of confused hues, and of residual hues.
Figure 3.
Uniform hue-difference circles for six color order systems or uniform color spaces (UCS): Munsell, DIN, OSA-UCS, Nickerson (started for OSA but never completed as a UCS), CIELUV, and CIELAB.
The circles (as 360 degree hue angle circles) are compared in terms of wavelength (x-axis) and distribution of wavelength nm per 5 degree hue angle (y-axis) for monochromatic or boundary colors. The x-axis covers the full hue circle from mid-purple (530 c) through the spectrum to mid-purple again. Nonspectral hues are shown to arbitrary scale (from [26]). Dotted vertical lines at 442 and 613 nm indicate limits to the effective spectrum for monochromatic optimal color stimuli. From Pridmore [26].
Figure 4.
Mean luminous efficiency curves in log for protanopes, deuteranopes, tritanopes, and normal trichromats (dashed line, for CIE 1924 V(λ)).
For clarity, three of the curves are displaced down by one log unit each. Redrawn from Pitt [13] and Wright [23].
Figure 5.
Calculated b and y chromatic response curves (b as negative portion, y as positive portion) for protanopes (P, in red) and deuteranopes (D, in green), redrawn from Hurvich & Jameson [35].
The curves intersect the zero line at 489 and 498 nm and their wavelength peaks are about 540 and 565 nm. Superimposed in gray are spectral sensitivity curves for M and L cones. In deuteranopia, yellow hues derive from the L cone curve (peak 565 nm) and its product the y chromatic response (see [36]), whose peak is also 565 nm. These are missing in protanopia and replaced by the M cone and its g chromatic response. All functions indicate shorter wavelength peaks and operating ranges for protanopia than deuteranopia.
Figure 6.
CIELUV uniform color space showing protanope (red line), deuteranope (green line), and tritanope (blue) confusion loci.
The neutral point wavelengths are 493, 498 and 568 nm (Table 1), whose complementaries are the confusion point wavelengths. Orthogonal (dashed) lines indicate residual hue complementary pairs at 567–430, ca. 469–572, and 494–494 c. Illuminant is D65.
Figure 7.
CIELUV hue circle circumscribed around the D65 illuminant point in CIELUV diagram (Fig. 6).
All wavelengths retain same hue angle (from say the vertical) as in Fig 6. Indicated lines and wavelengths are transferred from Fig. 6. Common range of each unique hue (asterisks) is approximated by colored arrows outside the hue circle.
Figure 8.
Protanopic, deuteranopic and tritanopic main confusion loci shown in Munsell hue circle for CIE Illuminant C (at Value 5 and max achievable Chroma).
As in Figures 6–7, orthogonal dashed loci indicate residual hue pairs as complementary wavelengths. The inexact complementarity of Munsell space (note the indicated angles of 75 and 105 degrees which should both be 90) compromises the orthogonal relations apparent in CIELUV space (Figure 6).
Figure 9.
CIELUV uniform color space as in Figure 6 but for “sunlight” Illuminant B.
Shows protanope confusion locus (red line) from 495.5 nm-495.5 c, and its resultant orthogonal (dashed red line) measured as 571-435 nm (predicting residual hues), deuteranope confusion locus (green line) from 500.4 nm-500.4 c and its orthogonal measured as 470–575 nm (residual hues), and tritanope confusion locus (blue line) from 571 nm-571c/435 nm and its resultant orthogonal 495.7 nm-495.7c (residual hues).
Figure 10.
CIELUV uniform color space as in Figure 9 but for “sunlight” Illuminant D50.
Shows protanope confusion locus (red line) from 495.5 nm-495.5 c, and its resultant orthogonal measured as 570–432 nm (predicting residual hues), deuteranope confusion locus (green line) from 500.4 nm-500.4 c and its orthogonal 470.3–574 nm (residual hues), and (blue line) tritanope confusion locus 571–450 nm and its orthogonal 496 nm-496 c (residual hues).
Figure 11.
CIELUV hue circle as for Figure 7 but for Illuminant D50.
Shows Protan, Deuteran, and Tritan confusion loci and their neutral point wavelengths 495.5, 500.4, 571 nm, transferred from Figure 10 CIELUV diagram, with their orthogonals (dashed lines) predicting the residual hues.
Figure 12.
As Figure 7 (for Illum D65) but with Figure 11 (Illum D50) superimposed.
The latter's lines and wavelengths are shown in black and inside the hue circle to compare with Figure 7′s wavelengths labeled outside the hue circle. Note similar angles between corresponding loci in Figures 7 and 11 despite different wavelengths, with Figure 11′s loci shifted angularly slightly clockwise relative to Figure 7′s loci, indicating chromatic adaptation.
Table 2.
Color constancy between illuminants D65 and D50.