Rochester Institute of Technology RIT Scholar Works Theses 8-1-1994 Visual assessment of object color chroma and colorfulness Jason Peterson Follow this and additional works at: https://scholarworks.rit.edu/theses Recommended Citation Peterson, Jason, "Visual assessment of object color chroma and colorfulness" (1994). Thesis. Rochester Institute of Technology. Accessed from This Thesis is brought to you for free and open access by RIT Scholar Works. It has been accepted for inclusion in Theses by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. ROCHESTER INSTITUTE OF TECHNOLOGY This volume is the property of the Institute, but the literary rights of the author must be respected. Please refer to permission statement in this volume for denial or permission, by author, to reproduce. In addition, if the reader obtains any assistance from this volume, he must give proper credit in his own work. This thesis has been used by the following persons, whose signatures attest to their acceptance of the above restrictions. Name Address Date COPYRIGHT REV. 10/93 THESIS RELEASE PERMISSION FORM ROCHESTER INSTITUTE OF TECHNOLOGY COLLEGE OF IMAGING ARTS AND SCIENCES Title of Thesis: Visual Assessment of Object Color Chroma andColorfulness I, Jason W. Peterson, give permission for reproductions to be made of this Thesis. Date: July 11, 1994 ACKNOWLEDGEMENTS The Author wishes to extend his deep thanks to the following individuals: Roy Berns, Mark Fairchild and Lisa Reniff for their direction and patience. Hatsumi Hung for hours of cheerful experimental observations. Mark Fairchild for the use of his computer program of the Nayatani color appearance model. Jeff Wang and Ken Parton for their encouragement to finish. Dana Marsh and all the staff at the Center for Imaging Science who facilitated the completion of my studies at RIT. Macbeth for their donation of fluorescent daylight simulator tubes. ABSTRACT A series of visual experiments were designed to determine whether naive observers typically evaluate chroma or colorfulness when judging color appearance. A total of 7 observers were asked to determine a color appearance match between Munsell samples under the same illuminant (C) at different levels of illuminance. Color appearance matches were determined for 12 Munsell samples, under five reference and matching scene illuminance conditions, for four experimental techniques. The four experimental techniques were haploscopic, simultaneous inspection, successive inspection, and short-term memory matching. Results suggested that a chroma match was most important when observers were evaluating the color appearance of two scenes at different levels of illuminance. Results were also compared to predictions of two color appearance models. While similar trends were apparent between the experimental results and the two model's predictions, only the Hunt model's chroma term satisfactorily predicted experimental observations. TABLE OF CONTENTS 1.0 Introduction 1 2.0 Background 3 2.1 The Study of Color Appearance 4 2.2 Literature Review 5 3.0 Color Appearance Models 48 3.1 The Hunt Model 49 3.2 The Nayatani Model 51 4.0 Analysis of Experimental Techniques 53 4.1 Haploscopic Matching 53 4.2 Magnitude Estimation 54 4.3 Memory Scaling 55 5.0 Experimental 56 5.1 Pilot Experimental Apparatus 57 5.2 Pilot Experimental Procedure 63 5.3 Pilot Experiment 1: Haploscopic Matching 64 5.4 Pilot Experiment 2: Matching by Simultaneous Inspection 65 5.5 Pilot Experimental Results 65 5.6 Final Experimental Design 66 5.7 Experimental Apparatus 67 5.8 Experimental Procedure 71 5.9 Observers 75 5.10 Experiment 1: Haploscopic Matching 75 5.11 Experiment 2: Matching by Simultaneous Inspection 76 5.12 Experiment 3: Matching by Successive Inspection 77 5.13 Experiment 4: Short Term Memory Matching 80 TABLE OF CONTENTS (continued) 6.0 Discussion 81 7.0 Conclusion 105 8.0 References 106 Appendix A: Color appearance estimations of seven observers Ill Appendix B: Color Appearance estimations of observer H.H 120 Appendix C: Descriptive statistics for observer's estimations 129 Appendix D: Fortran computer program of the Hunt color appearance model 141 Appendix E: Experimental results transformed by the Hunt and Nayatani models 145 Appendix F: Plots of color appearance model predictions of experimental observations averaged across Munsell hue 152 Appendix G: Hunt and Nayatani Predictions for each Munsell sample and illuminance condition 156 Appendix H: Light Booth spectroradiometric data 158 LIST OF FIGURES 2-1. Helson's color booth 7 2-2. Binocular viewing apparatus used by Wassef. 18 2-3. MacAdam's differential retinal conditioning apparatus 19 2-4. Test pattern used by Jameson and Hurvich 23 2-5. Relationship between luminance and estimated brightness 24 2-6. Complex scene used by Pitt and Winter 32 2-7. Valberg's haploscopic matching apparatus 33 2.8. Hunt and Winter's adaptation apparatus 35 2.9. Breneman's complex target 36 2.10. Breneman's viewing apparatus 38 2.11. Viewing conditions used by Troscianko 40 2.12. Visual fields used by Richter 45 2-13. Chromatic adaptation apparatus used by Breneman 46 3-1. Schematic diagram of Nayatani model 52 5-1. Reference scene used in pilot experiments 58 5-2. Hunt and Nayatani color appearance model predictions 59 5-3. Matching scene used in pilot experiments 61 5-4. Reference scene used in final experiments 68 5-5. Matching scene used in final experiments 70 5-6. How the reference and matching scenes appeared to observers 72 5-7. Viewing arrangement used in successive inspection technique 79 6-1. Model predictions of haploscopic experiment 87 6-2. Model predictions of simultaneous inspection experiment 87 6-3. Model predictions of successive inspection experiment 88 6-4. Model predictions of value 3/ samples (haploscopic technique) 91 6-5. Model predictions of value 5/ samples (haploscopic technique) 91 6-6. Model predictions of value 7/ samples (haploscopic technique).... 92 6-7. Model predictions of value 3/ samples (simultaneous inspection) 92 6-8. Model predictions of value 5/ samples (simultaneous inspection) 93 6-9. Model predictions of value 7/ samples (simultaneous inspection) 93 6-10. Model predictions of value 3/ samples (successive inspection) 94 6-11. Model predictions of value 5/ samples (successive inspection) 94 6-12. Model predictions of value 7/ samples (successive inspection) 95 6-13. Haploscopic results compared to Nayatani predictions 98 6-14. Simultaneous inspection results compared to Nayatani predictions 100 6-15. Successive inspection results compared to Nayatani predictions 100 LIST OF TABLES 2-1. Helson's illumination conditions 8 2-2. Background illuminances used by Helson, Judd, and Warren 15 2-3. Adapting luminances used by Hunt 16 2-4. Adapting conditions used by MacAdam 19 2-5. Illuminance levels used by Breneman 47 5-1. Illumination levels used for the pilot experiments 64 5-2. Illumination levels for final experiments 73 5-3. Munsell notations of reference samples used in condition 1 74 5-4. Munsell notations of reference samples used in conditions 2 through 5 74 5-5 Average observer error in test condition 82 5-6. Average standard deviations for each technique and illuminance level 82 INTRODUCTION The need to predict the color appearance of objects has necessitated terminology to describe how the attributes of a color change with changes in illumination and surround. This terminology has evolved into present CIE definitions for lightness, brightness, colorfulness, saturation, and chroma (among others). The CIE definitions for each of these terms are provided below. Brightness: An attribute of visual sensation according to which an area appears to emit more or less light Lightness: The brightness of an area judged relative to the brightness of a similarly illuminated area that appears white highly transmitting. Colorfulness: An attribute of visual sensation according to which the perceived color of an area appears to be more or less chromatic. Saturation: The colorfulness of an area judged as a proportion of its brightness. Chroma: The colorfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting. These definitions have thoughtfully and conveniently been written to describe how color appearance can be judged in the context of a scene or surround. While such terminology is very useful during visual experiments, outside the laboratory color appearance is usually evaluated in a purely intuitive fashion. The convenience of color appearance terminology belies the fact that very little is known about the method with which color appearance is typically assessed, and the conditions under which that method of assessment might change. The need for research regarding methods used for color appearance assessment is apparent in the field of color reproduction. Recently a great deal of effort has been directed toward hardcopy reproductions of softcopy displays. Because the luminance differences between softcopy and hardcopy images can be large, and the resulting color gamut that the two image types have in common is small, color reproduction is made difficult at best. If it were possible to determine those viewing conditions when relative color appearance was most important (CIE lightness and chroma), and those conditions when absolute color appearance was most important (CIE brightness and colorfulness), it would provide a useful starting point. Recent models designed to predict