Rita M. Halsey and A. Chapanis, "An Experimental Determination of Some Iso-Chromaticity Lines in Color-Deficient Vision*," J. Opt. Soc. Am. 42, 722-739 (1952)
From an assortment of red and red-purple Munsell papers, 47 color-deficient and 13 color-normal subjects selected matches for eight standard blue-green and neutral papers. The color-deficient subjects were classified into the following groups: 7 protans with severe defects, 9 protans with mild defects, 10 deutans with severe defects, and 21 deutans with mild defects. For every subject the three colors (one at each of three chroma levels) chosen as matches for each standard were plotted on the CIE diagram, and a straight line, originating at the locus of the standard color, was fitted through the points. The slopes of these lines are significantly different for protans and deutans. Color-deficient subjects with mild defects tend to select the same matches as do those with severe defects, but the former show more variability. In addition, matches made by subjects with severe defects are more often rated “good” or “excellent,” and are more likely to fall along a straight line than are those made by subjects with mild defects. Matches made by the color-normal subjects are most variable and never rated good. Data on the constants of the iso-chromaticity lines, the Munsell notations of the matches, and the lightness relationships are given. For all matches by deutans and for matches against neutral standards by protanopes, the agreement of the empirical lines with those predicted from spectral data by Judd is good. However, protan matches against blue-green standards diverge markedly from predictions; protans actually select colors which are yellower than those predicted from spectral data. When the data for all value levels are pooled, it appears that the iso-color lines for some subjects may be curved rather than straight.
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Matches which were rated good and excellent for each of the standard colors by the two groups of color-deficient subjects. The first numeral following each Munsell hue designation shows the number of subjects who rated a particular match excellent; the numeral in parentheses shows the number of additional subjects who rated a particular match good.
Chroma /2
Chroma /4
Chroma /6
Standards
Protans
Deutans
Protans
Deutans
Protans
Deutans
5 RP 2/2
1(1)
5 RP 2/2
−(2)
2.5 R 2/4
−(1)
7.5 RP 3/4
3(3)
10 RP 2/6
−(2)
7.5 RP 3/6
−(3)
10 RP 3/2
1(4)
5 RP 3/2
−(4)
2.5 R 3/4
−(1)
10 RP 3/4
6(7)
2.5 R 2/6
−(1)
10 RP 2/6
−(1)
N 3/
2.5 R 3/2
−(2)
7.5 RP 3/2
1(5)
2.5 R 4/4
−(1)
2.5 R 2/4
−(2)
2.5 R 3/6
1(1)
10 RP 3/6
−(1)
5 R 3/2
2(1)
10 RP 2/2
−(2)
7.5 R 2/4
−(1)
2.5 R 4/6
−(1)
10 RP 3/2
−(2)
7.5 RP 4/2
1(−)
2.5 RP 4/2
−(1)
10 RP 4/4
−(1)
5 RP 3/4
−(1)
10 RP 3/6
−(1)
7.5 RP 4/6
4(1)
N 4/
10 RP 4/2
4(3)
5 RP 4/2
−(1)
5 RP 4/4
−(1)
10 RP 5/6
−(2)
10 RP 4/6
−(1)
2.5 R 4/2
−(2)
7.5 RP 4/2
7(8)
7.5 RP 4/4
4(5)
2.5 R 5/6
−(1)
2.5 R 5/2
−(1)
7.5RP 5/2
1(−)
10 RP 4/4
−(2)
5 RP 5/2
−(2)
5 RP 5/2
1(3)
10 RP 5/4
3(4)
5 RP 5/4
1(1)
7.5 RP 5/6
−(1)
7.5 RP 5/6
3(3)
N 5/
7.5 RP 5/2
2(−)
7.5 RP 5/2
11(8)
7.5 RP 5/4
5(7)
10 RP 5/6
1(1)
10 RP 5/2
−(7)
10 RP 6/6
−(1)
2.5 R 5/2
1(1)
5 RP 6/2
3(1)
5 RP 6/2
12(6)
7.5 RP 6/4
−(1)
5 RP 6/4
6(7)
10 RP 6/6
1(1)
5 RP 6/6
3(2)
N 6/
7.5 RP 6/2
2(2)
7.5 RP 6/2
−(3)
10 RP 5/4
−(1)
7.5 RP 6/4
−(3)
10 RP 7/6
−(1)
7.5 RP 6/6
1(2)
10 RP 6/2
4(3)
10 RP 6/4
−(5)
10 RP 6/4
−(1)
10 RP 7/4
−(1)
5 R 3/2
−(1)
5 RP 3/2
1(−)
5 R 4/4
−(1)
5 RP 3/4
4(−)
5 R 4/6
−(2)
5 RP 3/6
2(4)
2.5 BG 3/6
7.5 R 4/2
−(1)
7.5 RP 3/2
3(3)
7.5 RP 3/4
−(1)
7.5 RP 3/6
−(2)
10 R 4/2
1(−)
10 RP 3/2
−(1)
10 RP 3/4
−(1)
2.5 R 3/6
−(1)
7.5 R 5/2
1(3)
10 P 4/2
−(1)
7.5 R 5/4
1(3)
2.5 RP 4/4
−(1)
5 R 5/6
−(1)
5 RP 4/6
2(2)
2.5 BG 4/6
5 RP 4/2
3(3)
5 RP 4/4
1(−)
7.5 RP 4/2
1(1)
2.5 BG 5/6
5 RP 5/2
3(3)
7.5 R 6/4
−(4)
5 RP 5/4
−(2)
5 RP 5/6
1(−)
10 RP 5/2
−(1)
10 R 6/4
−(1)
7.5 RP 5/4
1(−)
7.5 RP 5/6
3(3)
7.5 R 7/2
1(3)
5 RP 6/2
2(2)
7.5 R 7/4
6(1)
7.5 RP 6/4
−(1)
5 R 7/6
1(−)
5 RP 6/6
3(−)
2.5 BG 6/6
10 RP 6/2
−(1)
10 R 7/4
1(−)
10 RP 6/4
−(1)
7.5 R 7/6
3(2)
7.5 RP 6/6
1(2)
2.5 R 6/2
−(1)
Table II
Constants of the best-fitting straight lines computed for the three color matches made with each standard color by each subject. The entries are the slopes of the lines which originate at the points given at the head of each column. Slopes in ordinary type identify lines which are good fits, those in italics fair fits, those in parentheses poor fits, to the data. Within each group (except the color normal), subjects are listed roughly in order of decreasing severity of color deficiency. Subjects marked with asterisks had very mild defects and could not be classified with certainty.
Wavelengths of the intercepts of the confusion lines with the spectrum or purple locus for protans and deutans with severe defects, good fits only. Complementary wavelengths are computed relative to standard source C, x=0.310, y=0.316.
Standards
Protans
Deutans
N 3/
492 c
497 c
N 4/
493 c
496 c
N 5/
493 c
496 c
N 6/
493 c
498 c
2.5 BG 3/6
623
497 c
2.5 BG 4/6
622
495 c
2.5 BG 5/6
621
496 c
2.5 BG 6/6
631
497 c
Table IV
Slopes of the best-fitting straight lines computed for matches rated excellent, and those rated good and excellent by the subjects concerned (see Table I).
Average reflectances,
, of the Munsell chips (three for each subject) selected as matches for each standard color. Reflectances of the standard colors are shown at the head of each column.
Standard colors
N 3/
N 4/
N 5/
N 6/
2.5 BG 3/6
2.5 BG 4/6
2.5 BG 5/6
2.5 BG 6/6
Reflectances of the standards
0.0651
0.121
0.191
0.303
0.0762
0.139
0.215
0.343
Protans with severe defects
0.0708
0.171
0.224
0.331
0.129
0.219
0.302
0.434
Protans with mild defects
0.0702
0.174
0.238
0.346
0.135
0.245
0.324
0.422
Deutans with severe defects
0.0724
0.138
0.207
0.333
0.0794
0.154
0.222
0.328
Deutans with mild defects
0.0620
0.131
0.213
0.348
0.0807
0.153
0.224
0.335
Color-normal subjects
0.0584
0.131
0.208
0.325
0.0886
0.152
0.251
0.345
Table VI
Summary of correlations among measures.
Protans
Deutans
Color normal
Severe
Mild
Severe
Mild
Average rank-order intercorrelation
Slopes
+0.69
+0.49
+0.47
+0.50
+0.61
Reflectances
+0.22
+0.44
+0.08
+0.25
+0.40
Rank-order correlation
Slopes vs reflectances
+0.75
+0.13
+0.02
+0.54
−0.16
Slopes vs red thresholds
+0.74
+0.04
+0.04
+0.21
+0.57
Reflectances vs red thresholds
+0.40
−0.02
−0.14
+0.13
−0.09
Table VII
Comparison of the slopes of the iso-chromaticity lines found in this study against the slopes predicted from data obtained with spectrum colors.
From Table II.
From Table IV.
Computed from Judd, reference 2; see also Fig. 1.
Computed from Judd, reference 13.
Tables (7)
Table I
Matches which were rated good and excellent for each of the standard colors by the two groups of color-deficient subjects. The first numeral following each Munsell hue designation shows the number of subjects who rated a particular match excellent; the numeral in parentheses shows the number of additional subjects who rated a particular match good.
Chroma /2
Chroma /4
Chroma /6
Standards
Protans
Deutans
Protans
Deutans
Protans
Deutans
5 RP 2/2
1(1)
5 RP 2/2
−(2)
2.5 R 2/4
−(1)
7.5 RP 3/4
3(3)
10 RP 2/6
−(2)
7.5 RP 3/6
−(3)
10 RP 3/2
1(4)
5 RP 3/2
−(4)
2.5 R 3/4
−(1)
10 RP 3/4
6(7)
2.5 R 2/6
−(1)
10 RP 2/6
−(1)
N 3/
2.5 R 3/2
−(2)
7.5 RP 3/2
1(5)
2.5 R 4/4
−(1)
2.5 R 2/4
−(2)
2.5 R 3/6
1(1)
10 RP 3/6
−(1)
5 R 3/2
2(1)
10 RP 2/2
−(2)
7.5 R 2/4
−(1)
2.5 R 4/6
−(1)
10 RP 3/2
−(2)
7.5 RP 4/2
1(−)
2.5 RP 4/2
−(1)
10 RP 4/4
−(1)
5 RP 3/4
−(1)
10 RP 3/6
−(1)
7.5 RP 4/6
4(1)
N 4/
10 RP 4/2
4(3)
5 RP 4/2
−(1)
5 RP 4/4
−(1)
10 RP 5/6
−(2)
10 RP 4/6
−(1)
2.5 R 4/2
−(2)
7.5 RP 4/2
7(8)
7.5 RP 4/4
4(5)
2.5 R 5/6
−(1)
2.5 R 5/2
−(1)
7.5RP 5/2
1(−)
10 RP 4/4
−(2)
5 RP 5/2
−(2)
5 RP 5/2
1(3)
10 RP 5/4
3(4)
5 RP 5/4
1(1)
7.5 RP 5/6
−(1)
7.5 RP 5/6
3(3)
N 5/
7.5 RP 5/2
2(−)
7.5 RP 5/2
11(8)
7.5 RP 5/4
5(7)
10 RP 5/6
1(1)
10 RP 5/2
−(7)
10 RP 6/6
−(1)
2.5 R 5/2
1(1)
5 RP 6/2
3(1)
5 RP 6/2
12(6)
7.5 RP 6/4
−(1)
5 RP 6/4
6(7)
10 RP 6/6
1(1)
5 RP 6/6
3(2)
N 6/
7.5 RP 6/2
2(2)
7.5 RP 6/2
−(3)
10 RP 5/4
−(1)
7.5 RP 6/4
−(3)
10 RP 7/6
−(1)
7.5 RP 6/6
1(2)
10 RP 6/2
4(3)
10 RP 6/4
−(5)
10 RP 6/4
−(1)
10 RP 7/4
−(1)
5 R 3/2
−(1)
5 RP 3/2
1(−)
5 R 4/4
−(1)
5 RP 3/4
4(−)
5 R 4/6
−(2)
5 RP 3/6
2(4)
2.5 BG 3/6
7.5 R 4/2
−(1)
7.5 RP 3/2
3(3)
7.5 RP 3/4
−(1)
7.5 RP 3/6
−(2)
10 R 4/2
1(−)
10 RP 3/2
−(1)
10 RP 3/4
−(1)
2.5 R 3/6
−(1)
7.5 R 5/2
1(3)
10 P 4/2
−(1)
7.5 R 5/4
1(3)
2.5 RP 4/4
−(1)
5 R 5/6
−(1)
5 RP 4/6
2(2)
2.5 BG 4/6
5 RP 4/2
3(3)
5 RP 4/4
1(−)
7.5 RP 4/2
1(1)
2.5 BG 5/6
5 RP 5/2
3(3)
7.5 R 6/4
−(4)
5 RP 5/4
−(2)
5 RP 5/6
1(−)
10 RP 5/2
−(1)
10 R 6/4
−(1)
7.5 RP 5/4
1(−)
7.5 RP 5/6
3(3)
7.5 R 7/2
1(3)
5 RP 6/2
2(2)
7.5 R 7/4
6(1)
7.5 RP 6/4
−(1)
5 R 7/6
1(−)
5 RP 6/6
3(−)
2.5 BG 6/6
10 RP 6/2
−(1)
10 R 7/4
1(−)
10 RP 6/4
−(1)
7.5 R 7/6
3(2)
7.5 RP 6/6
1(2)
2.5 R 6/2
−(1)
Table II
Constants of the best-fitting straight lines computed for the three color matches made with each standard color by each subject. The entries are the slopes of the lines which originate at the points given at the head of each column. Slopes in ordinary type identify lines which are good fits, those in italics fair fits, those in parentheses poor fits, to the data. Within each group (except the color normal), subjects are listed roughly in order of decreasing severity of color deficiency. Subjects marked with asterisks had very mild defects and could not be classified with certainty.
Wavelengths of the intercepts of the confusion lines with the spectrum or purple locus for protans and deutans with severe defects, good fits only. Complementary wavelengths are computed relative to standard source C, x=0.310, y=0.316.
Standards
Protans
Deutans
N 3/
492 c
497 c
N 4/
493 c
496 c
N 5/
493 c
496 c
N 6/
493 c
498 c
2.5 BG 3/6
623
497 c
2.5 BG 4/6
622
495 c
2.5 BG 5/6
621
496 c
2.5 BG 6/6
631
497 c
Table IV
Slopes of the best-fitting straight lines computed for matches rated excellent, and those rated good and excellent by the subjects concerned (see Table I).
Average reflectances,
, of the Munsell chips (three for each subject) selected as matches for each standard color. Reflectances of the standard colors are shown at the head of each column.
Standard colors
N 3/
N 4/
N 5/
N 6/
2.5 BG 3/6
2.5 BG 4/6
2.5 BG 5/6
2.5 BG 6/6
Reflectances of the standards
0.0651
0.121
0.191
0.303
0.0762
0.139
0.215
0.343
Protans with severe defects
0.0708
0.171
0.224
0.331
0.129
0.219
0.302
0.434
Protans with mild defects
0.0702
0.174
0.238
0.346
0.135
0.245
0.324
0.422
Deutans with severe defects
0.0724
0.138
0.207
0.333
0.0794
0.154
0.222
0.328
Deutans with mild defects
0.0620
0.131
0.213
0.348
0.0807
0.153
0.224
0.335
Color-normal subjects
0.0584
0.131
0.208
0.325
0.0886
0.152
0.251
0.345
Table VI
Summary of correlations among measures.
Protans
Deutans
Color normal
Severe
Mild
Severe
Mild
Average rank-order intercorrelation
Slopes
+0.69
+0.49
+0.47
+0.50
+0.61
Reflectances
+0.22
+0.44
+0.08
+0.25
+0.40
Rank-order correlation
Slopes vs reflectances
+0.75
+0.13
+0.02
+0.54
−0.16
Slopes vs red thresholds
+0.74
+0.04
+0.04
+0.21
+0.57
Reflectances vs red thresholds
+0.40
−0.02
−0.14
+0.13
−0.09
Table VII
Comparison of the slopes of the iso-chromaticity lines found in this study against the slopes predicted from data obtained with spectrum colors.