We analyze the sources of error in specifying color in CRT displays. Theseinclude errors inherent in the use of the color matching functions of theCIE 1931 standard observer when only colorimetric, not radiometric, calibrationsare available. We provide transformation coefficients that prove to correctthe deficiencies of this observer very well. We consider four different candidatesets of cone sensitivities. Some of these differ substantially; variationamong candidate cone sensitivities exceeds the variation among phosphors.Finally, the effects of the recognized forms of observer variation on thevisual responses (cone excitations or cone contrasts) generated by CRT stimuliare investigated and quantitatively specified. Cone pigment polymorphism givesrise to variation of a few per cent in relative excitation by the differentphosphors—a variation larger than the errors ensuing from the adoptionof the CIE standard observer, though smaller than the differences betweensome candidate cone sensitivities. Macular pigmentation has a larger influence,affecting mainly responses to the blue phosphor. The estimated combined effectof all sources of observer variation is comparable in magnitude with the largestdifferences between competing cone sensitivity estimates but is not enoughto disrupt very seriously the relation between the L and M cone weights andthe isoluminance settings of individual observers. It is also comparable withtypical instrumental colorimetric errors, but we discuss these only briefly.
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Article tables are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Mean and StandardDeviation of the CIE 1931 Chromaticity Coordinates for the Sampled Monitors
Chromaticity Coordinate
Phosphor Type
Red
Green
Blue
x
0.620 (±0.009)
0.288 (±0.011)
0.153 (±0.004)
y
0.342 (±0.006)
0.597 (±0.008)
0.070 (±0.004)
Table 2
Rms ErrorsResulting from Use of the 1931 CIE Color Matching Functionswith the Transformation Specified in Eq. (3)a
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0004
0.0010
0.0028
M
0.0005
0.0011
0.0021
S
0.0089
0.0078
0.0064
Each value is the rms of the errors in the estimatedL, M, or S cone excitations for any individual monitor, expressed as a fractionof the average excitation for all monitors.
Table 3
Maximum ErrorsResulting from Use of the 1931 CIE Color Matching Functions with the TransformationSpecified in Eq. (3)a
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0006
0.0026
0.0053
M
0.0009
0.0026
0.0039
S
0.0263
0.0147
0.0126
Each value is the maximum error in the estimatedL, M, or S cone excitations for any individual monitor, expressed as a fractionof the average excitation for all monitors.
Table 4
Rms Errorsin Chromaticity and Luminance Resulting from Use of the 1931 CIE Color MatchingFunctions with the Transformation Specified in Eq. (3)a
Colorimetric Measure
Phosphor Type
Red
Green
Blue
l
0.00004
0.00002
0.00031
s
0.00909
0.00882
0.00755
Y
0.00039
0.00106
0.00250
Each value is the rms of the errors in the estimated l, s, or Y forany individual monitor, expressed as a fraction of the average value of l, s, or Y forall monitors.
Table 5
Rms ErrorsResulting from Observer Variation in Visual Pigment Absorption Spectra forOur Average Monitor Phosphorsa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0417
-0.0008
-0.0158
M
0.0363
0.0062
-0.0100
S
0.0293
0.0552
0.0200
Each value is the fractional change in the estimatedL, M, or S cone excitations when the corresponding wavelength of peak absorption,
is increased by 1 standard deviation;if negative signs are disregarded, the values are the rms fractional variationsacross observers in cone excitation that result from observer variation in
Table 6
Changes inCone Excitations Resulting from Displacements of Visual Pigment AbsorptionSpectraa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0278
-0.0005
-0.0105
M
0.0404
0.0069
-0.0111
S
0.0366
0.0690
0.0250
Each value is the fractional increment in the estimatedL, M, or S cone excitations when the corresponding peak absorption is increasedby 1 nm.
Table 7
Rms ErrorsResulting from Individual Variation in Macular Pigmentationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0037
0.0272
0.1764
M
0.0152
0.0375
0.2080
S
0.2715
0.2341
0.2829
Each value is the rms of the fractional changes inthe estimated L, M, or S cone excitations due to observer variation in macularpigmentation
Table 8
Rms ErrorsResulting from Individual Variation in Lens Pigmentationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0067
0.0209
0.0408
M
0.0122
0.0231
0.0447
S
0.0718
0.0499
0.0787
Each value is the rms of the fractional changes inthe estimated L, M, or S cone excitations due to observer variation in lenspigmentation.
Table 9
Rms ErrorsResulting from Individual Variation in Visual Pigment Densitya
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0797
0.0624
0.0780
M
0.0831
0.0643
0.0751
S
0.0755
0.0874
0.0710
Each value is the rms of the fractional changes inthe estimated L, M, or S cone excitations due to observer variation in visualpigment density.
Table 10
Rms ErrorsResulting from Individual Variation in Visual Pigment Densitya
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0045
-0.0127
0.0028
M
0.0079
-0.0109
0.0000
S
0.0003
0.0122
-0.0042
This differs from Table 9because changes common to all cone excitations and all phosphors are discountedhere by normalization with the same scaling factor.
Table 11
Rms ErrorsResulting from All Sources of Individual Variation
Cone Type
Phosphor Type
Red
Green
Blue
L
0.1417
0.1161
0.0501
M
0.1287
0.1046
0.0741
S
0.1364
0.1029
0.1489
Table 12
Rms ErrorsResulting from all Sources of Individual Variationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0
0.0491
0.1839
M
0.0385
0
0.1665
S
0.0149
0.0624
0
For each cone type, changes common to all phosphorsare discounted by normalization. Thus the values indicate individual variationof cone contrast instead of variation of absolute cone excitation.
Table 13
FractionalChanges in Sensation Luminance of the Red and Blue PhosphorRelative to That of the Green Phosphor Resulting from Different Sourcesof Individual Variationa
Source of Variation
Phosphor Type
Red
Blue
L cone
0.0362
-0.0085
M cone
0.0037
-0.0064
Macular pigmentdensity
0.0249
-0.1751
Lens density
0.0139
-0.0211
Visual pigmentdensity
0.0175
0.0133
Total rmsvariation
0.0494
0.1772
Each value is the fractional increment in sensationluminance when the corresponding physiological factor is increased by 1 standarddeviation.
Table 14
Rms ErrorsResulting from Measurement-Device Variationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0116
0.0129
0.0128
M
0.0432
0.0171
0.0651
S
0.0995
0.0601
0.1344
Based on the differences between a trifilter colorimeterand a spectroradiometer measured by Shepherd.12 Differences in luminance have been corrected for (see text).Each value is the rms of the differences of the two devices in L, M, or Scone excitations for two monitors, expressed as a fraction of the averagespectroradiometrically determined excitation for both monitors.
Tables (14)
Table 1
Mean and StandardDeviation of the CIE 1931 Chromaticity Coordinates for the Sampled Monitors
Chromaticity Coordinate
Phosphor Type
Red
Green
Blue
x
0.620 (±0.009)
0.288 (±0.011)
0.153 (±0.004)
y
0.342 (±0.006)
0.597 (±0.008)
0.070 (±0.004)
Table 2
Rms ErrorsResulting from Use of the 1931 CIE Color Matching Functionswith the Transformation Specified in Eq. (3)a
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0004
0.0010
0.0028
M
0.0005
0.0011
0.0021
S
0.0089
0.0078
0.0064
Each value is the rms of the errors in the estimatedL, M, or S cone excitations for any individual monitor, expressed as a fractionof the average excitation for all monitors.
Table 3
Maximum ErrorsResulting from Use of the 1931 CIE Color Matching Functions with the TransformationSpecified in Eq. (3)a
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0006
0.0026
0.0053
M
0.0009
0.0026
0.0039
S
0.0263
0.0147
0.0126
Each value is the maximum error in the estimatedL, M, or S cone excitations for any individual monitor, expressed as a fractionof the average excitation for all monitors.
Table 4
Rms Errorsin Chromaticity and Luminance Resulting from Use of the 1931 CIE Color MatchingFunctions with the Transformation Specified in Eq. (3)a
Colorimetric Measure
Phosphor Type
Red
Green
Blue
l
0.00004
0.00002
0.00031
s
0.00909
0.00882
0.00755
Y
0.00039
0.00106
0.00250
Each value is the rms of the errors in the estimated l, s, or Y forany individual monitor, expressed as a fraction of the average value of l, s, or Y forall monitors.
Table 5
Rms ErrorsResulting from Observer Variation in Visual Pigment Absorption Spectra forOur Average Monitor Phosphorsa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0417
-0.0008
-0.0158
M
0.0363
0.0062
-0.0100
S
0.0293
0.0552
0.0200
Each value is the fractional change in the estimatedL, M, or S cone excitations when the corresponding wavelength of peak absorption,
is increased by 1 standard deviation;if negative signs are disregarded, the values are the rms fractional variationsacross observers in cone excitation that result from observer variation in
Table 6
Changes inCone Excitations Resulting from Displacements of Visual Pigment AbsorptionSpectraa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0278
-0.0005
-0.0105
M
0.0404
0.0069
-0.0111
S
0.0366
0.0690
0.0250
Each value is the fractional increment in the estimatedL, M, or S cone excitations when the corresponding peak absorption is increasedby 1 nm.
Table 7
Rms ErrorsResulting from Individual Variation in Macular Pigmentationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0037
0.0272
0.1764
M
0.0152
0.0375
0.2080
S
0.2715
0.2341
0.2829
Each value is the rms of the fractional changes inthe estimated L, M, or S cone excitations due to observer variation in macularpigmentation
Table 8
Rms ErrorsResulting from Individual Variation in Lens Pigmentationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0067
0.0209
0.0408
M
0.0122
0.0231
0.0447
S
0.0718
0.0499
0.0787
Each value is the rms of the fractional changes inthe estimated L, M, or S cone excitations due to observer variation in lenspigmentation.
Table 9
Rms ErrorsResulting from Individual Variation in Visual Pigment Densitya
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0797
0.0624
0.0780
M
0.0831
0.0643
0.0751
S
0.0755
0.0874
0.0710
Each value is the rms of the fractional changes inthe estimated L, M, or S cone excitations due to observer variation in visualpigment density.
Table 10
Rms ErrorsResulting from Individual Variation in Visual Pigment Densitya
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0045
-0.0127
0.0028
M
0.0079
-0.0109
0.0000
S
0.0003
0.0122
-0.0042
This differs from Table 9because changes common to all cone excitations and all phosphors are discountedhere by normalization with the same scaling factor.
Table 11
Rms ErrorsResulting from All Sources of Individual Variation
Cone Type
Phosphor Type
Red
Green
Blue
L
0.1417
0.1161
0.0501
M
0.1287
0.1046
0.0741
S
0.1364
0.1029
0.1489
Table 12
Rms ErrorsResulting from all Sources of Individual Variationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0
0.0491
0.1839
M
0.0385
0
0.1665
S
0.0149
0.0624
0
For each cone type, changes common to all phosphorsare discounted by normalization. Thus the values indicate individual variationof cone contrast instead of variation of absolute cone excitation.
Table 13
FractionalChanges in Sensation Luminance of the Red and Blue PhosphorRelative to That of the Green Phosphor Resulting from Different Sourcesof Individual Variationa
Source of Variation
Phosphor Type
Red
Blue
L cone
0.0362
-0.0085
M cone
0.0037
-0.0064
Macular pigmentdensity
0.0249
-0.1751
Lens density
0.0139
-0.0211
Visual pigmentdensity
0.0175
0.0133
Total rmsvariation
0.0494
0.1772
Each value is the fractional increment in sensationluminance when the corresponding physiological factor is increased by 1 standarddeviation.
Table 14
Rms ErrorsResulting from Measurement-Device Variationa
Cone Type
Phosphor Type
Red
Green
Blue
L
0.0116
0.0129
0.0128
M
0.0432
0.0171
0.0651
S
0.0995
0.0601
0.1344
Based on the differences between a trifilter colorimeterand a spectroradiometer measured by Shepherd.12 Differences in luminance have been corrected for (see text).Each value is the rms of the differences of the two devices in L, M, or Scone excitations for two monitors, expressed as a fraction of the averagespectroradiometrically determined excitation for both monitors.