Measuring Colour
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Series Preface xvii
Preface xix
Acknowledgements xxi
1 Colour Vision 1
1.1 Introduction 1
1.2 The spectrum 1
1.3 Construction of the eye 3
1.4 The retinal receptors 4
1.5 Spectral sensitivities of the retinal receptors 5
1.6 Visual signal transmission 8
1.7 Basic perceptual attributes of colour 9
1.8 Colour constancy 10
1.9 Relative perceptual attributes of colours 11
1.10 Defective colour vision 13
1.11 Colour pseudo-stereopsis 15
2 Spectral Weighting Functions 19
2.1 Introduction 19
2.2 Scotopic spectral luminous efficiency 19
2.3 Photopic spectral luminous efficiency 21
2.4 Colour-matching functions 26
2.5 Transformation from R, G, B to X, Y, Z 32
2.6 CIE colour-matching functions 33
2.7 Metamerism 38
2.8 Spectral luminous efficiency functions for photopic vision 39
3 Relations between Colour Stimuli 41
3.1 Introduction 41
3.2 The Y tristimulus value 41
3.3 Chromaticity 42
3.4 Dominant wavelength and excitation purity 44
3.5 Colour mixtures on chromaticity diagrams 46
3.6 Uniform chromaticity diagrams 48
3.7 CIE 1976 hue-angle and saturation 51
3.8 CIE 1976 lightness, L 52
3.9 Uniform colour spaces 53
3.10 CIE 1976 colour difference formulae 57
3.11 CMC, CIE94, and CIEDE2000 color difference formulae 61
3.12 An alternative form of the CIEDE2000 colour-difference equation 64
3.13 Summary of measures and their perceptual correlates 64
3.14 Allowing for chromatic adaptation 65
3.15 The evaluation of whiteness 66
3.16 Colorimetric purity 67
3.17 Identifying stimuli of equal brightness 67
3.18 CIEDE2000 worked example 69
4 Light Sources 73
4.1 Introduction 73
4.2 Methods of producing light 74
4.3 Gas discharges 74
4.4 Sodium lamps 75
4.5 Mercury lamps 76
4.6 Fluorescent lamps 78
4.7 Xenon lamps 81
4.8 Incandescent light sources 82
4.9 Tungsten lamps 86
4.10 Tungsten halogen lamps 87
4.11 Light emitting diodes 88
4.12 Daylight 89
4.13 Standard illuminants and sources 91
4.14 CIE standard illuminant A 91
4.15 CIE illuminants B and C 92
4.16 CIE sources 93
4.17 CIE illuminants D 94
4.18 CIE indoor daylight 94
4.19 Comparison of commonly used sources 96
5 Obtaining Spectral Data and Tristimulus Values 99
5.1 Introduction 99
5.2 Radiometry and photometry 99
5.3 Spectroradiometry 100
5.4 Tele-spectroradiometry 100
5.5 Spectroradiometry of self-luminous colours 101
5.6 Spectrophotometry of non-self-luminous colours 101
5.7 Reference whites and working standards 102
5.8 Geometries of illumination and viewing 103
5.9 CIE Geometries of illumination and measurement 104
5.10 Spectroradiometers and spectrophotometers 108
5.11 Choice of illuminant 110
5.12 Calculation of tristimulus values from spectral data 111
5.13 Colorimeters using filtered photo-detectors 114
6 Metamerism and Colour Constancy 117
6.1 Introduction 117
6.2 The cause of metamerism 117
6.3 The definition of metamerism 118
6.4 Examples of metamerism in practice 119
6.5 Degree of metamerism 121
6.6 Index of metamerism for change of illuminant 122
6.7 Index of metamerism for change of observer 122
6.8 Index of metamerism for change of field size 124
6.9 Colour matches and geometry of illumination and measurement 124
6.10 Correcting for inequalities of tristimulus values 125
6.11 Terms used in connection with metamerism 126
6.12 Colour inconstancy 127
6.13 Chromatic adaptation transforms 129
6.14 The Von Kries transform 130
6.15 The CAT02 transform 131
6.16 A colour inconstancy index 134
6.17 Worked examples 135
7 Colour Rendering by Light Sources 143
7.1 Introduction 143
7.2 The meaning of colour rendering 144
7.3 CIE colour rendering indices 145
7.4 Spectral band methods 147
7.5 Other methods for assessing the colour rendering of light sources 150
7.6 Comparison of commonly used sources 151
8 Colour Order Systems 155
8.1 Introduction 155
8.2 Variables 155
8.3 Optimal colours 157
8.4 TheMunsell System 159
8.5 TheMunsell Book of Color 164
8.6 Unique hues and colour opponency 168
8.7 The Natural Colour System (NCS) 170
8.8 Natural Colour System Atlas 172
8.9 The DIN System 179
8.10 The Coloroid System 182
8.11 The Optical Society of America (OSA) System 183
8.12 The Hunter Lab System 187
8.13 The Tintometer 190
8.14 The Pantone System 191
8.15 The RAL System 191
8.16 Advantages of colour order systems 192
8.17 Disadvantages of colour order systems 192
9 Precision and Accuracy in Colorimetry 197
9.1 Introduction 197
9.2 Sample preparation 198
9.3 Thermochromism 199
9.4 Geometry of illumination and measurement 199
9.5 Reference white calibration 200
9.6 Polarisation 200
9.7 Wavelength calibration 202
9.8 Stray light 202
9.9 Zero level and linearity 202
9.10 Use of secondary standards 203
9.11 Bandwidth 203
9.12 Correcting for errors in the spectral data 204
9.13 Calculations 207
9.14 Precautions to be taken in practice 214
10 Fluorescent Colours 219
10.1 Introduction 219
10.2 Terminology 219
10.3 Use of double monochromators 220
10.4 Illumination with white light 221
10.5 Correcting for differences between an actual and the desired source 222
10.6 Two-monochromator method 224
10.7 Two-mode method 225
10.8 Filter-reduction method 226
10.9 Luminescence-weakening method 226
10.10 Practical considerations 227
11 RGB Colorimetry 231
11.1 Introduction 231
11.2 Choice and specification of matching stimuli 231
11.3 Choice of units 233
11.4 Chromaticity diagrams using r and g 233
11.5 Colour-matching functions in RGB systems 234
11.6 Derivation of XYZ from RGB tristimulus values 35
11.7 Using television and computer displays 239
12 Colorimetry with Digital Cameras 241
12.1 Introduction 241
12.2 Camera characterisation 242
12.3 Metamerism 244
12.4 Characterisation methods 244
12.5 Practical considerations in digital camera characterisation 249
12.6 Practical example 251
12.7 Discussion 254
13 Colorant Mixtures 257
13.1 Introduction 257
13.2 Non-diffusing colorants in a transmitting layer 257
13.3 Non-diffusing colorants in a layer in optical contact with a diffusing surface 259
13.4 Layers containing colorants which diffuse and absorb light 262
13.5 The use of multi-spectral analysis to reduce metamerism in art restoration 264
14 Factors Affecting the Appearance of Coloured Objects 267
14.1 Introduction 267
14.2 Measuring optical properties 267
14.3 Colour 268
14.4 Gloss 271
14.5 Translucency 279
14.6 Surface texture 281
14.7 Conclusions 289
15 The CIE Colour Appearance Model CIECAM02 293
15.1 Introduction 293
15.2 Visual areas in the observing field 294
15.3 Chromatic adaptation in CIECAM02 294
15.4 Spectral sensitivities of the cones in CIECAM02 295
15.5 Cone dynamic response functions in CIECAM02 297
15.6 Luminance adaptation in CIECAM02 297
15.7 Criteria for achromacy and for constant hue in CIECAM02 299
15.8 Effects of luminance adaptation in CIECAM02 300
15.9 Criteria for unique hues in CIECAM02 303
15.10 Redness-greenness, a, and yellowness-blueness, b, in CIECAM02 303
15.11 Hue angle, h, in CIECAM02 305
15.12 Eccentricity factor, e, in CIECAM02 305
15.13 Hue quadrature, H, and hue composition, Hc, in CIECAM02 306
15.14 The achromatic response, A, in CIECAM02 308
15.15 Correlate of lightness, J, in CIECAM02 308
15.16 Correlate of brightness, Q, in CIECAM02 309
15.17 Correlate of chroma, C, in CIECAM02 310
15.18 Correlate of colourfulness, M, in CIECAM02 311
15.19 Correlate of saturation, s, in CIECAM02 311
15.20 Comparison of CIECAM02 with the natural colour system 311
15.21 Testing model CIECAM02 312
15.22 Filtration of projected slides and CIECAM02 314
15.23 Comparison of CIECAM02 with CIECAM97s 315
15.24 Uniform colour space based on CIECAM02 315
15.25 Some problems with CIECAM02 316
15.26 Steps for using the CIECAM02 model 316
15.27 Steps for using the CIECAM02 model in reverse mode 319
15.28 Worked example for the model CIECAM02 321
16 Models of Colour Appearance for Stimuli of Different Sizes 325
16.1 Introduction 325
16.2 Stimuli of different sizes 325
16.3 Room colours 325
16.4 A model for predicting room colours 326
16.5 Steps in using the model for predicting room colours 327
17 Model of Colour Appearance for Unrelated Colours in Photopic and Mesopic Illuminances 329
17.1 Introduction 329
17.2 A model for predicting unrelated colours 330
17.3 Input data required for the model 331
17.4 Steps in using the model for unrelated colours 332
17.5 Worked example in the model for predicting unrelated colours 333
Appendices 335
Appendix 1 Radiometric and Photometric Terms and Units 337
A1.1 Introduction 337
A1.2 Physical detectors 337
A1.3 Photometric units and terms 338
A1.4 Radiant and quantum units and terms 340
A1.5 Radiation sources 340
A1.6 Terms for measures of reflection and transmission 341
A1.7 Other spectral luminous efficiency functions 343
A1.8 Mesopic photometry 343
Reference 344
Appendix 2 Spectral Luminous Efficiency Functions 345
Appendix 3 CIE Colour-Matching Functions 347
Appendix 4 CIE Spectral Chromaticity Co-Ordinates 351
Appendix 5 Relative Spectral Power Distributions of Illuminants 355
A5.1 Introduction 355
A5.2 CIE illuminants 355
A5.3 Representative fluorescent lamps 359
A5.4 Planckian radiators 368
A5.5 Gas discharge lamps 371
A5.6 Method of calculating D illuminant distributions 374
Appendix 6 Colorimetric Formulae 379
A6.1 Chromaticity relationships 379
A6.2 CIELUV, CIELAB, and U*V*W* relationships 379
Appendix 7 Calculation of the CIE Colour Rendering Indices 383
A7.1 Spectral radiance factors of test colours 383
A7.2 Worked example of the CIE colour rendering indices 388
Appendix 8 Illuminant-Observer Weights for Calculating Tristimulus Values 393
Appendix 9 Glossary of Terms 431
Reference 453
Index 455
