1 2 Colour measurement 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 43X i © Woodhead Publishing Limited, 2010 1 The Textile Institute and Woodhead Publishing 2 3 The Textile Institute is a unique organisation in textiles, clothing and footwear. 4 Incorporated in England by a Royal Charter granted in 1925, the Institute has individual and corporate members in over 90 countries. The aim of the Institute is to 5 facilitate learning, recognise achievement, reward excellence and disseminate 6 information within the global textiles, clothing and footwear industries. 7 Historically, The Textile Institute has published books of interest to its members 8 and the textile industry. To maintain this policy, the Institute has entered into 9 partnership with Woodhead Publishing Limited to ensure that Institute members and 10 the textile industry continue to have access to high calibre titles on textile science and 1 technology. Most Woodhead titles on textiles are now published in collaboration with The 2 Textile Institute. Through this arrangement, the Institute provides an Editorial Board which advises Woodhead on appropriate titles for future publication and suggests possible editors and authors for these books. Each book published under this arrangement carries the Institute’s logo. Woodhead books published in collaboration with The Textile Institute are offered to Textile Institute members at a substantial discount. These books, together with those published by The Textile Institute that are still in print, are offered on the Woodhead website at: www.woodheadpublishing.com. Textile Institute books still in print are also available directly from the Institute’s website at: www.textileinstitutebooks.com A list of Woodhead books on textile science and technology, most of which have been published in collaboration with The Textile Institute, can be found on pages xv–xxi. 1 2 3 4 5 6 7 8 9 40 1 2 43X ii © Woodhead Publishing Limited, 2010 Woodhead Publishing Series in Textiles: Number 103 1 2 3 4 Colour measurement 5 6 7 Principles, advances 8 9 and industrial applications 10 1 2 3 Edited by 4 5 M. L. Gulrajani 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 Oxford Cambridge Philadelphia New Delhi 43X iii © Woodhead Publishing Limited, 2010 1 Published by Woodhead Publishing Limited in association with The Textile Institute 2 Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington 3 Cambridge CB21 6AH, UK www.woodheadpublishing.com 4 5 Woodhead Publishing, 525 South 4th Street #241, Philadelphia, PA 19147, USA 6 Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, 7 Daryaganj, New Delhi-110002, India 8 www.woodheadpublishingindia.com 9 10 First published 2010, Woodhead Publishing Limited © Woodhead Publishing Limited, 2010 1 The authors have asserted their moral rights. 2 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials. Neither the authors nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfi lming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specifi c permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identifi cation and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN 978-1-84569-559-0 (print) ISBN 978-0-85709-019-5 (online) 1 ISSN 2042-0803 Woodhead Publishing Series in Textiles (print) 2 ISSN 2042-0811 Woodhead Publishing Series in Textiles (online) 3 4 The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using 5 acid-free and elemental chlorine-free practices. Furthermore, the publisher ensures that 6 the text paper and cover board used have met acceptable environmental accreditation 7 standards. 8 Typeset by Refi neCatch Limited, Bungay, Suffolk, UK 9 Printed by TJI Digital, Padstow, Cornwall, UK 40 1 2 43X iv © Woodhead Publishing Limited, 2010 11 2 Contents 3 4 5 6 7 8 9 10 1 2 Contributor contact details xi 3 Woodhead Publishing Series in Textiles xv 4 5 6 Part I Theories, principles and methods of 7 measuring colour 1 8 1 Colour vision: theories and principles 3 9 20 V. V. PÉREZ, D. DE FEZ SAIZ and F. MARTINEZ VERDÚ, 1 University of Alicante, Spain 2 1.1 Introduction 3 3 1.2 Human colour vision 6 4 1.3 Chromatic perception 10 5 1.4 Defective colour vision 12 6 1.5 Colour constancy 15 7 1.6 Bibliography 17 8 2 Scales for communicating colours 19 9 A. K. ROY CHOUDHURY, Government College of Engineering and 30 Textile Technology, India 1 2 2.1 Introduction 19 3 2.2 Systematic arrangements of colours 22 2.3 Colour order systems 23 4 2.4 Various colour order systems 31 5 2.5 Comparison and interrelation of various systems 51 6 2.6 Accuracy of colour order systems 54 7 2.7 Computer-based systems 54 8 2.8 Universal colour language (UCL) 61 9 2.9 Future trends 63 40 2.10 References 65 1 2 43X v © Woodhead Publishing Limited, 2010 vi Contents 1 3 Expressing colours numerically 70 2 V. C. GUPTE, Advanced Graphic Systems, India 3 3.1 Introduction 70 4 3.2 Colour specifi cations 70 5 3.3 The Commission Internationale de l’Eclairage (CIE) system 72 6 3.4 The CIE standard light sources/illuminants 72 7 3.5 The CIE Standard Observer and unreal primaries 74 8 3.6 Computation of tristimulus values 77 9 3.7 Refl ectance measurement 79 10 3.8 Chromaticity coordinates and chromaticity diagram 80 1 3.9 Usefulness of the CIE XYZ system 81 2 3.10 Limitations of the CIE system 82 3.11 Transformation and improvement of the CIE system 82 3.12 Future trends 86 3.13 References 86 4 Visual and instrumental evaluation of whiteness and yellowness 88 R. HIRSCHLER, SENAI/CETIQT Colour Institute, Brazil 4.1 Introduction: whiteness and yellowness 88 4.2 Visual assessment of whiteness 90 4.3 Measuring techniques and instruments 95 4.4 Indices for whiteness and yellowness 100 4.5 Applications in industry, cosmetics and dentistry 111 4.6 Future trends 115 4.7 Sources of further information and advice 117 4.8 References 119 5 U se of artifi cial neural networks (ANNs) in colour measurement 125 M. SENTHILKUMAR, PSG College of Technology, India 1 5.1 Introduction 125 2 5.2 Artifi cial neural networks (ANNs): basic principles 126 3 5.3 Architecture of an artifi cial neural network 127 4 5.4 Learning process 129 5 5.5 Feed-forward neural network 130 6 5.6 Training of an artifi cial neural network using back 7 propagation algorithm 130 8 5.7 Application of artifi cial neural networks to colour 9 measurement 132 40 5.8 Recipe prediction 135 1 5.9 Evaluation of the ANN method 140 2 5.10 Case studies 140 43X © Woodhead Publishing Limited, 2010 Contents vii 5.11 Future trends 141 1 5.12 Sources of further information and advice 144 2 5.13 References 144 3 4 6 Camera-based colour measurement 147 5 F. MARTÍNEZ-VERDÚ, E. CHORRO and E. PERALES, University of 6 Alicante, Spain, M. VILASECA and J. PUJOL, Technical University of 7 Catalonia, Spain 8 6.1 Introduction 147 9 6.2 Principles of camera-based colour measurement 149 10 6.3 Procedures of camera-based colour measurement 151 1 6.4 Strengths and weaknesses 154 2 6.5 Case studies 158 3 6.6 Future trends 162 4 6.7 Conclusions 163 5 6.8 Sources of further information and advice 163 6 6.9 References 163 7 8 7 Colour shade sorting 167 9 M. L. GULRAJANI, India Institute of Technology, India 20 7.1 Introduction 167 1 7.2 (555) Fixed-grid shade sorting system 168 2 7.3 Clemson Colour Clustering 174 3 7.4 K-means clustering 178 4 7.5 Modifi ed CCC shade sorting method 180 5 7.6 Shade sequencing and clustering 180 6 7.7 References 182 7 8 8 D etermining uncertainty and improving the 9 accuracy of color measurement 184 30 J. A. LADSON, Color Science Consultancy, USA 1 8.1 Introduction to determining uncertainty 184 2 8.2 Uncertainty 185 3 8.3 Defi nitions 186 4 8.4 Tables of results 187 5 8.5 Conclusions: determining uncertainty 189 6 8.6 Improving accuracy: the absolute correction of 7 instrumentally generated spectrometer values 190 8.7 Introduction to improving accuracy 190 8 8.8 Experimental modeling 191 9 8.9 Applications 193 40 8.10 Conclusions: improving accuracy 194 1 8.11 References 195 2 43X © Woodhead Publishing Limited, 2010 viii Contents 1 9 Colour measurement and fastness assessment 196 2 M . BIDE, Department of Textiles, Fashion Merchandising and 3 Design, University of Rhode Island, USA 4 9.1 Introduction: colour and colourfastness 196 5 9.2 The use and usefulness of colourfastness testing 197 6 9.3 Colourfastness test method development 199 7 9.4 Colourfastness test standard setting organizations 200 8 9.5 Standard colourfastness test format 201 9 9.6 Testing for colourfastness: specifi c tests 203 10 9.7 Colourfastness testing: assessment of results 1 (colour measurement) 207 2 9.8 Conclusions 216 9.9 References 216 Part II Colour measurement and its applications 219 10 Colour measurement methods for textiles 221 N. S. GANGAKHEDKAR, Compute Spectra Color Pvt. Ltd., India 10.1 Introduction 221 10.2 Colour as numbers 222 10.3 Colour specifi cation 224 10.4 Metamerism 226 10.5 Reasons why colours do not match 231 10.6 Visual versus numerical pass/fail 232 10.7 Colour measurement techniques for textiles 236 10.8 On-line colour measurement 242 10.9 Colour of dry and wet fabrics 247 10.10 Inspection of colour of fi nished fabrics: a case study 248 10.11 Future trends 250 10.12 Conclusions 250 10.13 Sources of further information and advice 251 1 10.14 References 251 2 3 11 Grading of cotton by color measurement 253 4 B. XU, The University of Texas, USA 5 11.1 History of cotton color grading 253 6 11.2 USDA cotton color grades 253 7 11.3 HVI colorimeter 254 8 11.4 Factors affecting cotton color grade 255 9 11.5 Color measurement using color image analysis 259 40 11.6 Using neural networks 263 1 11.7 Using fuzzy logic 268 2 11.8 Conclusions 276 43X 11.9 References 277 © Woodhead Publishing Limited, 2010 Contents ix 12 Colour measurement of paint fi lms and coatings 279 1 N. S. GANGAKHEDKAR, Compute Spectra Color Pvt. Ltd., India 2 12.1 Introduction 279 3 12.2 Quality control of paints 280 4 12.3 Sample preparation for colour measurement 291 5 12.4 Pigment quality control 292 6 12.5 Problems in match prediction: paint applications 295 7 12.6 Computer colour matching for paints 295 8 12.7 Colour control system 297 9 12.8 Measuring colour properties of wet paints 299 10 12.9 Instant colour matching at the paint shop 300 1 12.10 Colour matching of automotive paints 307 2 12.11 Future trends 309 3 12.12 Conclusions 309 4 12.13 Sources of further information and advice 310 5 12.14 References 310 6 7 13 Colour measurement of food: principles and practice 312 8 D. B. MACDOUGALL, Formerly of the University of Reading, UK 9 13.1 Introduction 312 20 13.2 Colour vision: trichromatic detection 313 1 13.3 The infl uence of ambient light and food structure 316 2 13.4 Appearance 317 3 13.5 Absorption and scatter 318 4 13.6 Colour description: the CIE system 319 5 13.7 Colour description: uniform colour space 320 6 13.8 Instrumentation 325 7 13.9 Food colour appearance measurement in practice 327 8 13.10 Illuminant spectra and uniform colour 336 9 13.11 Conclusions and future trends 337 30 13.12 References 339 1 14 Colorimetric evaluation of tooth colour 343 2 3 A. JOINER, Unilever Oral Care, UK 4 14.1 Introduction 343 5 14.2 The human dentition and its environment 344 6 14.3 Optical properties of teeth 345 7 14.4 The colour of teeth 347 14.5 Factors that impact tooth colour and its perception 348 8 14.6 Tooth whiteness 351 9 14.7 Measurement of tooth colour 352 40 14.8 Measurement of extrinsic stain 356 1 14.9 Methods to improve tooth colour 357 2 14.10 Future trends 361 43X © Woodhead Publishing Limited, 2010