THE MEASUREMENT OF APPEARANCE

Transcription

1 THE MEASUREMENT OF APPEARANCE Second Edition RICHARD S. HUNTER RICHARD W. HAROLD Hunter Associates Laboratory, Inc. Reston, Virginia A WILEY-INTERSCIENCE PUBLICATION JOHN WILEY & SONS New York / Chichester / Brisbane / Toronto / Singapore

2 PART ONE APPEARANCE ATTRIBUTES AND THEIR BASES IN PHYSICS, PSYCHOLOGY, AND PHYSIOLOGY 1 ATTRIBUTES OF THE APPEARANCE OF OBJECTS 3 Evaluating Light 4 Modes of Appearance 5 Evaluating the Appearance of Objects 7 Color Attributes 7 Color Order Systems 10 Ostwald 10 Geometric Attributes 13 DIFFUSE AND SPECULAR LIGHT DISTRIBUTIONS 13 Classification of Objects (The Sub-Modes) 16 2 LIGHT SOURCES AND ILLUMINATION 20 What Is Light? 20 Luminosity 21 Describing Light Spectrally 23 Light Sources 24 Incandescent Sources 24 Other Sources 25 Illuminants 28 3 INTERACTION OF OBJECTS WITH LIGHT 29 What Objects Do to Light 29 Ehe Optical Similarities of Different Products 33 The Relation Between Absorption and Scattering 35

3 Physical Evaluation of Light from Objects 37 Spectrophotometric Curves 38 Goniophotometric Curves 41 4 THE HUMAN OBSERVER AND VISUAL EVALUATION OF OBJECT APPEARANCE 51 The Human Observer 51 Color Vision 51 Visual Sensitivity to Light Signals 53 The Capabilities of the Human Observer 54 Visual Evaluation of Appearance 55 Spectral Conditions 55 Geometric Conditions 55 Light Intensity 56 Summary of Conditions to Be Controlled 57 Standardized Conditions for Visual Evaluation of Color 57 Light Sources and Illuminants 57 Artificial Daylight Illuminants 61 Lighting Arrangement and Placement of Specimens 63 Standardized Conditions for Visual Evaluation of Gloss 64 General Rules for Visual Examination 66 5 PSYCHOPHYSICAL SCALES FOR APPEARANCE MEASUREMENT 68 Psychophysics and Appearance Scales 68 PART TWO THE DEVELOPMENT OF NUMERICAL SPECIFICATIONS FOR APPEARANCE ATTRIBUTES SCALES FOR GLOSS AND OTHER GEOMETRIC ATTRIBUTES 75 Gloss 75 Established Methods to Measure Gloss 82 Limitations of Instrumental Methods for Measuring Gloss 89 Surface Texture 89

4 xi Transparent Materials 90 Opacity 90 7 THE CIE STANDARD OBSERVERS 95 Luminosity 95 Additive and Subtractive Color Mixing 96 Analyzing the Wavelength Response Characteristics of Observers 97 Transformations 100 The Standard Observer 100 Using the Standard Observer Functions 101 Object Color Computations for X, Y, Z 103 THE WEIGHTED-ORDINATE INTEGRATION METHOD 103 THE SELECTF.n-ORDINATF. INTEGRATION METHOD 104 INSTRUMENT AUTOMATIC INTEGRATION 104 Metamerism 106 CIL Chromaticity 107 The Chromaticity Diagram 107 Adapting CIE Specifications to Object Colors 111 The Y, x, у Color Solid, Defined by the MacAdam Limits 114 The CIE Supplementary Standard Observer 116 Summary of Terms UNIFORM COLOR SCALES 119 Lightness Perception and Uniform Lightness Scales 121 The Development of Uniform Color Scales 123 Wavelength and Purity Discriminations and the Judd Series of Scales 125 Judd Uniform Chromaticity Scale Triangle 126 MacAdam u,v Diagram 128 breckenridge and Schaub: RUCS 129 Hunter Alpha-Beta Diagram and L',a',ß' Color Solid 131 The CIE 1964 U*V*W* and CIE 1976 L*u*v* Systems 133 CIE 1976 L*u*v* (CIELUV) Color Space 135 Munsell Based Scales 135 Adams: Chromatic Value and Chromatic Valence 136 Adams-Nickerson and Modified Adams-Nicker son Scales 139 Hunter Rd, a, b and L, a, b Scales 141

5 Glasser Cube Root 142 CIE 1976 L* a* b* 143 CIE 1976 L* a* b* (CIELAB) Color Space 145 CIE 1976 Correlates of Perceived Lightness, Chroma, and Hue 146 Scale-Expansion Coefficients for L, a, and /; Type Opponent-Colors Scales 148 MacAdam-Base Scales The MacAdam-Friele Group 153 MacAdam (P,Q,S) and the EMC Metric 154 Other Uniform Color Scales 155 Intercomparison of Color Scales 156 Interconversion Among Color Scales 158 Selection of Color Scales 158 SCALES FOR THE MEASUREMENT OF COLOR DIFFERENCE 162 Concept of Color Difference 163 The Historical Development of Methods of Color-Difference Measurement 164 Munsell System Color-Difference Scales 167 Adams-Nickerson Series 169 Judd-Hunter Systems 170 MacAdam Systems 175 CIE 1976 Recommendations 177 The JPC79 and CMC(/:c) Colour-Difference Formulas 180 Interrelationships of Color Difference Scales 183 Factors Affecting Visual Color Difference Evaluations 185 Variables Affecting Visual and Instrumental Estimates of Color Difference 186 Selection of Methods of Color Difference Measurement 189 Levels of Color Difference Discrimination 189 Nonsymmetry of Color Tolerances 191 Necessity for High Precision 191 Metamerism Indexes 193 SPECIAL SCALES FOR WHITE COLORS 195 The Optics of White Materials 195 Measurement Scales for Whites 199 Luminous Reflectance Factor Y or Lightness L 201

6 xiii Blue Reflectance Factor В 203 Yellowness Index YI 205 Whiteness Index Wl 206 Graphic Techniques OTHER SCALES FOR COLOR IDENTIFICATION 209 Single-Number Golor Scales for Specific Products 209 Single-Number Scales for Yellowness of Amber-Colored Liquids and Resins 210 Scales Used to Measure Color Quality of Specific Food Products 214 Color Identification by Subtractive Color Mixture 218 Lovibond Color System and Tintometer 218 Densitometry and the Subtractive-Mixture Color Solid 220 Color Identification by Additive Color Mixture 224 Visual Additive Colorimeters 226 Disk Colorimetry 226 Collections of Colored Chips for Identification of Colors of Surfaces; Color-Order Systems 227 Munsell Color System 227 ISCC-NBS System of Color Names 231 Oslwald Color System 231 The DIN Color System 233 The Natural Colour System 234 The Ridgway Color Standards and Color Nomenclature 236 Maen and Raul Dictionary 237 PART THREE INSTRI;MENTS FOR THE MEASUREMENT OK APPEARANCE 12 INSTRUMENT CLASSIFICATION AND COMPONENTS 241 Instrument Types 242 Spectral and Geometric Factors of Instrument Design 243 Light Sources 246 Incandescent Light Sources 246 Fluorescent Lamps 249

7 Xenon Arc Lamps 249 Lasers 249 Geometrie Design Illuminating and Viewing Beams of Light 250 Directions of Light Beams 250 Spatial Dimensions of Light Beams 254 Vignetting 256 Parallel- and Converging-Beam Configurations 257 The Specimen and Its Window 257 Equal Weighting of all Permitted Light Rays 258 Interchange of Directions of Illumination and View 258 Precision of One- and Two-Beam Configurations 259 Spectral Design Wavelength Selection Devices and Photodetectors 259 Wavelength-Selection Devices 260 NARROW- AND BROADBAND WAVELENGTH SELECTION 263 FILTER COMBINATIONS 264 Light Detectors 264 HUMAN EYE 264 Photodetectors 265 PHOTOEMLSSIVF. DETECTORS 265 PHOTOVOLTAIC CELLS 266 PHOTOCONDUCTIVE CELLS 268 Electrical Measurement Devices 270 Measuring Systems for Signal Analysis 270 Data Display Devices 271 INSTRUMENTS FOR THE GEOMETRIC ATTRIBUTES OF OBJECT APPEARANCE 273 Cioniophotometers 273 Historical Background 275 Goniophotometer Design 275 Uses of Goniophotometers 276 Diffuse Reflection Meters 276 Historical Background 276 Reflectometer Design 278 Uses of Diffuse Reflection Meters 279 DENSITOMETERS (REFLECTION AND TRANSMISSION) 280

8 Specular Gloss and Reflection Meters 281 Historical Background 281 Glossmeter Design 282 Use of Specular Glossmeters 283 Direction-Contrast Meters for Contrast Gloss, Distinctnessof-Image Gloss, and Reflection Haze 284 Lustermeter for Measurement of Contrast Gloss 285 üistinctness-oj-reflected-1 mage and Reflection-Haze Meters 285 Instruments for Transmission Measurements 287 Haze Meters 287 Clarity Meters, Turbidimeters, Transmission Opacimeters 287 INSTRUMENTS FOR THE CHROMATIC ATTRIBUTES OF OBJECT APPEARANCE 290 Spectrophotometers 290 Design Features of Spectrophotometers 292 WAVELENGTH ISOLATION AND IDENTIFICATION 292 SPECIMEN ILLUMINATION AND VIEWING 293 Use of the Spectrophotometry: Output 296 CONVERSION OF SPECTRAL CURVES TO TRISTIMULUS X, Y, Z VALUES 296 COLOR FORMULATION BY SPECTROPHOTOMETRY AND COMPUTER 296 Tristimulus Instruments Reflectometers and Colorimeters 296 Historical Background 297 Tristimulus Colorimeters 297 DESIGN OF COLORIMETERS 299 LIGHT SOURCES 299 LIGHT RECEIVERS THE PHOTODE I ECTORS 301 INSTRUMENT READOUTS 301 USES OF TRISTIMULUS INSTRUMENTS 302 STANDARDS, STANDARDIZATION, AND MEASUREMENT TECHNIQUES 303 Accuracy and Precision 303 Ideal or Perfect Standards References 304 Primary Standards 305

9 Secondary Standards 306 Standards Materials 309 Care of Standards 314 Measurement Techniques SPECIMEN SELECTION, PREPARATION, AND PRESENTATION 316 Objectives in Specimen Preparation 318 Effects of Preparation on Specimen Properties 319 Requirements for Specimen Preparation Depending upon Type of Measurement to Be Made 320 Techniques for Handling Specimens of Different Forms 321 Benefits of the Specimen Averaging Technique APPLICATIONS OF APPEARANCE MEASUREMENTS 334 Importance of Product Appearance 334 Products and Industries Where Appearance Analyses Are Used 336 Uses of Measurements of Appearance Attributes 338 Identification 339 Tests for Conformity to Specifications 339 INCOMING RAW MATERIAL TESTING 339 MATERIALS IN PROCESS OF BEING MANUFACTURED 341 FINISHED MATERIAL READY FOR DELIVERY 341 Grading for Quality 343 Shade Sorting 344 Guiding or Adjusting Formulation of Product Color 348 Assessment of Product Performance in Service 354 Measurement of Nonappearance Variables 355 lest Methods for Appearance Analysis and Measurement 355 APPENDIX 361 BIBLIOGRAPHY/AUTHOR INDEX 381 GLOSSARY/SUBJECT INDEX 391