Identification and Assignment of Colorimetric Observer Categories and Their Applications in Color and Vision Sciences Abhijit Sarkar To cite this version: Abhijit Sarkar. Identification and Assignment of Colorimetric Observer Categories and TheirAp- plications in Color and Vision Sciences. Signal and Image processing. Université de Nantes, 2011. English. tel-00647246 HAL Id: tel-00647246 https://tel.archives-ouvertes.fr/tel-00647246 Submitted on 1 Dec 2011 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. UNIVERSITÉ DE NANTES Ecole polytechnique de l’Université de Nantes _____ ÉCOLE Année 2011 N° attribué par la bibliothèque Identification and Assignment of Colorimetric Observer Categories and Their Applications in Color and Vision Sciences ___________ THÈSE DE DOCTORAT Discipline : AUTOMATIQUE ET INFORMATIQUE APPLIQUEE Spécialité : TRAITEMENT DU SIGNAL ET DES IMAGES COULEUR Présentée et soutenue publiquement par Abhijit Sarkar Le 26 octobre 2011, devant le jury ci-dessous Président Mme. Sabine Süsstrunk Professeur, School of Computer and Communication Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Suisse Rapporteurs M. Mark Fairchild Professeur, Centre for Imaging Science, Rochester Institute of Technology, Etats-Unis Mme. Françoise Viénot Professeur MNHN (Muséum National d’Histoire Naturelle), Centre de Recherche sur la Conservation des Collections, Paris M. Laurent Bédat Maître de conférences, IETR, INSA de Rennes Examinateurs M. Patrick Le Callet Professeur, IRCCyN, Polytech Nantes, Université de Nantes M. Florent Autrusseau Ingénieur de Recherche, IRCCyN, Université de Nantes Invité M. Laurent Blondé Principal Scientist, Technicolor R&I, Rennes Directeur de thèse : M. Patrick Le Callet ED : ……………………. (Uniquement pour STIM et SPIGA) Acknowledgments Moving to France for a 3-year industrial PhD, and adjusting to a new culture with no prior knowledge of the language have been great adventures for me. The person who made a lot of things a lot easier was my supervisor at Technicolor R&I, Dr. Laurent Blondé. It is mainly because of him I survived the agonizing experiences with the exceedingly difficult French administrative system. He and his wonderful family helped me integrate with the French culture and lifestyle, a process that has been an amazing experience for me. On the professional front, Laurent played a critical part in bringing this thesis to the state where it stands today. I must also thank my colleagues, in particular Mr. Patrick Morvan and Dr. Jürgen Stauder, who extended a tremendous amount of support in every possible way throughout these years. I feel lucky to have had colleagues like them. I am also thankful to Technicolor management for allowing me all the freedom a corporate researcher can dream of. The guidance and supervision of my academic supervisors Prof. Patrick Le Callet and Dr. Florent Autrusseau at IRCCyN ensured my work remained focused and had adequate technical depth. I am also thankful for all their support at the personal level, particularly during my initial days in France. I would like to thank the members of my jury, Dr. Laurent Bédat, Prof. Mark Fairchild, Prof. Sabine Süsstrunk and Prof. Françoise Viénot, for accepting to be part of the committee. In particular, I am indebted to my reviewers, Prof. Fairchild and Prof. Viénot, for their valuable and comprehensive feedback on the thesis manuscript. Prof. Fairchild was my advisor at the Munsell Color Science Laboratory, and continues to be a source of inspiration. Prof. Viénot extended an incredible amount of help and advice during the final phase of my PhD, and I am highly appreciative of all the time she generously devoted to our numerous discussions. This research would not have been possible without the active participation and cooperation of all my 79 observers at Technicolor R&I, Rennes, at the Technische Universität Darmstadt, Germany and at the University of Veszprém, Hungary. I express my heartfelt gratitude to all of them. As I complete my eight years of graduate studies, I recall the unwavering support of my family for all these years − all the encouragement and inspiration that motivated me to chase my wild dreams. Finally, I would like to acknowledge Dr. Stefan Winkler for compiling a list of many wonderful quotations on his website, http://stefan.winkler.net/ , some of which I have used in this thesis. 2 Abstract The most fundamental aspect of applied colorimetry is the trichromacy of our visual system. Trichromacy leads to observer metamerism, in which two stimuli with very different spectral power distribution can produce a color match for a given observer, but will result in a mismatch for another observer with different color vision characteristics. This variability among observers with normal color vision poses a challenge to various modern industrial applications, including wide-gamut displays with narrow-band primaries, and Light-Emitting Diode (LED) or Laser based applications. Thus, the main objective of this thesis is to offer a practical solution to this problem for color-critical industrial applications. This work starts by conducting a comprehensive theoretical analysis on various aspects of the physiologically-based observer model (CIEPO06) proposed by the Technical Committee TC 1-36 of the Commission Internationale de l’Éclairage (CIE). In the context of color perception on modern narrow-band displays, the performances of the CIEPO06 model and of the CIE 10° standard colorimetric observer in predicting average Stiles and Burch (1959) observer data were evaluated. Some weaknesses of both observer models were identified, and an improvement of the CIEPO06 model was proposed based on a nonlinear optimization. In the next stage, several color-matching experiments were performed on two displays with very different spectral characteristics, one was a Cathode Ray Tube (CRT) display, and the other was a Liquid Crystal Display (LCD). The results confirmed the effect of observer metamerism in display color matches. Working toward a solution, a statistical analysis was performed on existing experimental and physiological datasets of color-matching functions. A set of eight colorimetric observer categories was proposed for use in color science and vision. Subsequently, an experimental observer classification method using two displays was developed. Through visual experiments it was proved that human observers with normal color vision can be classified into a small number of categories based on their color vision. This was followed by the development of a compact, inexpensive proof- of-concept prototype, described as the Observer Calibrator in this thesis. Using this prototype, two collaborative observer classification experiments involving a total of 49 observers were performed with researchers in Germany and Hungary. A correlation analysis was performed on observer classification data from the experiment in Germany, and suprathreshold color difference judgments obtained from an independent experiment involving the same set of observers. The consistency between observer categories and color difference data gave an indirect validation of the observer classification method. 3 Finally, an implementation of colorimetric observer categories in a practical color imaging workflow has been proposed. This workflow, described in this thesis as the observer dependent color imaging (ODCI), involves conversion of tristimulus values corresponding to CIE 10° standard colorimetric observer, into the tristimulus values corresponding to individual observer categories. Nonlinear transformations that result in accurate color transformations have been derived. The observer classification method, together with the compact and economical prototype, is the enabling factor for the practical implementation of observer dependent color imaging workflow in industrial applications. It is also hoped that the contributions of this thesis will be valuable for scientific research in the domains of color and vision sciences. 4 Table of Contents Acknowledgments .................................................................................................................................................. 2 Abstract................................................................................................................................................................... 3 Table of Contents.................................................................................................................................................... 5 1. Introduction .................................................................................................................................................. 10 1.1 Motivation .............................................................................................................................................. 10 1.2 Research hypothesis ............................................................................................................................... 11 1.3 Organization of the thesis ......................................................................................................................