Measuring Colour

by Hunt, R. W. G.; Pointer, M. R.

• ISBN13: 9781119975373
• ISBN10: 1119975379
• Edition: 4th
• Format: Hardcover
• Copyright: 2011-10-17
• Publisher: Wiley

Summary

The classic authority on colour measurement now fully revised and updated with the latest CIE recommendations The measurement of colour is of major importance in many commercial applications, such as the textile, paint, and foodstuff industries; as well as having a significant role in the lighting, paper, printing, cosmetic, plastics, glass, chemical, photographic, television, transport, and communication industries. Building upon the success of earlier editions, the 4th edition of [start italics]Measuring Colour[end italics] has been updated throughout with new chapters on colour rendering by light sources; colorimetry with digital cameras; factors affecting the appearance of coloured objects, and details of new CIE colour appearance models. Key features: Presents colour measurement, not simply as a matter of instrumentation and engineering, but also involving the physiology and psychology of the human observer. Covers the principles of colour measurement rather than a guide to instruments. Provides the reader with the basic facts needed to measure colour. Describes and explains the interactions between how colour is affected by the type of lighting, by the nature of the objects illuminated, and by the properties of the colour vision of observers. Includes many worked examples, and a series of Appendices provides the numerical data needed in many colorimetric calculations. The addition of 4th edition co-author, Dr. Pointer, has facilitated the inclusion of extensive practical advice on measurement procedures and the latest CIE recommendations.

Author Biography

Robert Hunt, Independent Colour Consultant and Visiting Professor, University of Leeds, UK Formerly Assistant Director of Research, Kodak Limited, Harrow; Dr. Hunt is now an independent colour consultant and a Visiting Professor at the University of Leeds' Department of Colour Science. He has written more than a hundred papers on colour vision, colour reproduction, and colour measurement. He has previously published the 6th edition of The Reproduction of Colour (2004) with Wiley which is viewed as a classic text on the topic. He has been awarded the Newton Medal of the Colour Group (Great Britain) (1974), the Progress Medal of the Royal Photographic Society (1984), the Judd-AIC Medal of the International Colour Association (1987), the Gold Medal of the Institute of Printing (1989), the Johann Gutenberg Prize of the Society for Information Display (2002), and the Godlove Award of the Inter-Society Color Council (U.S.A.) (2007). In 2009 he was given the award of Officer of the British Empire (O.B.E.).

Michael Pointer,  Independent Colour Consultant and Visiting Professor, University of Leeds, UK & University of the Arts London, UK Formerly Senior Scientist at the National Physical Laboratory, Teddington; Dr. Pointer is an independent colour consultant and a Visiting Professor at the University of Leeds' Department of Colour Science and the University of the Arts, London, in their School of Communication. In 1997, he received the Fenton Medal, The Royal Photographic Society's award for services to the Society. In 2004, he received a Silver Medal from the Society of Dyers and Colourists for 'contributions to colour science.' He has authored more than 95 scientific papers, is a Fellow of The Royal Photographic Society and the Institute of Physics, Secretary of CIE Division 1 Vision & Colour and UK Associate Editor of the journal, Color Research & Application.

Table of Contents

About the Authors xv

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