Color Science and Digital Imaging

Foreword...........................................................................................xv

Preface............................................................................................. xix

Acknowledgments............................................................................ xxiii

Introduction: The Five Spaces of the Digital Imaging Pipeline...........1

Chapter 1 - World Space..............................................................5

1.1 The Nature of Light....................................................................6

1.1.1 Wavelength............................................................................6

1.1.2 Amplitude..............................................................................7

1.1.3 Phase....................................................................................8

1.1.4 Polarization............................................................................8

1.1.5 Monochromatic Light.............................................................9

1.1.6 Coherent Light.......................................................................9

1.1.7 Particles............................................................................... 10

1.1.8 The Inverse Square Law...................................................... 10

1.1.9 Interior vs. Exterior Lighting.................................................. 11

1.2 Measuring Light...................................................................... 11

1.2.1 Candela (cd): The Brightness of a Light Source................... 12

1.2.2 Lumen (lm): The Total Amount of Incident Light................... 12

1.2.3 Lux (lx): How Brightly a Scene is Lit..................................... 12

1.2.4 Other Units.......................................................................... 13

1.3 Dynamic Range........................................................................ 13

1.3.1 Brightness vs. Luminance.................................................... 14

1.3.2 What is Dynamic Range?..................................................... 14

1.3.3 Stops................................................................................... 16

1.4 A Color Science Moment........................................................ 16

1.4.1 Emission Spectrums............................................................ 17

1.4.2 Spectral Reflectance............................................................ 17

1.4.3 Color Stimulus..................................................................... 18

1.5 Light Sources......................................................................... 19

1.5.1 Emission Spectrums............................................................ 19

1.5.2 Color Temperature...............................................................21

1.5.3 Standard Illuminants............................................................23

1.6 Surface Interactions with Light................................................ 24

1.6.1 Spectral Reflectance............................................................ 24

1.6.2 Diffuse vs. Specular Reflections...........................................26

1.7 Exotic Surface Interactions with Light.....................................27

1.7.1 Scattering............................................................................27

1.7.2 Polarized Light.....................................................................29

1.7.3 The Fresnel Effect................................................................30

1.7.4 Color from Interference........................................................32

1.7.5 Dichroic Filters.....................................................................33

1.8 How We See the World.........................................................33

1.8.1 Color Perception..................................................................34

1.8.2 CIE xy-chromaticity Diagram...............................................35

1.8.3 Our Visual Response...........................................................37

1.8.4 Adaptation...........................................................................38

1.8.4.1 General Brightness Adaptation.............................39

1.8.4.2 Lateral Brightness Adaptation...............................39

1.8.4.3 Chromatic Adaptation...........................................40

1.8.5 Calculating Luminance.........................................................40

1.8.6 Metamers............................................................................42

1.9 Conclusion.......................................................................................43

Chapter 2 - Camera Space....................................................................... 45

2.1 Camera Perceptions of Color...........................................................46

2.1.1 Spectral Sensitivity..............................................................46

2.1.2 Camera Gamuts..................................................................48

2.1.3 Converting Light to Digits.....................................................48

2.1.4 The Debayer Process..........................................................49

2.1.5 Camera Imaging Math......................................................... 51

2.1.6 Light Sources......................................................................52

2.1.6.1 Color Temperature................................................52

2.1.6.2 Spectral Emissions...............................................53

2.1.7 CCD vs. CMOS...................................................................54?

2.2 Space and Time...............................................................................56

2.2.1 Resolution...........................................................................56

2.2.2 ISO......................................................................................57

2.2.3 Speed..................................................................................57

2.2.4 Sensor Crop........................................................................59

2.2.5 Sensor Size.........................................................................60

2.2.6 Anamorphic Formats...........................................................62

2.2.6.1 Cinemascope 2.39................................................62

2.2.6.2 HDTV 1.33............................................................63

2.3 Camera Dynamic Range..................................................................63

2.3.1 Clipping...............................................................................64

2.3.2 Bit Depth.............................................................................65

2.4 Video Standards..............................................................................66

2.4.1 Resolutions..........................................................................66

2.4.1.1 HDTV Standards ....................................................................66

2.4.1.2 UHDTV Standards ....................................................................67

2.4.2 Scan Modes........................................................................67

2.4.2.1 Progressive Scan..................................................67

2.4.2.2 Interlaced Scan.....................................................67

2.4.2.3 History..................................................................69

2.4.3 Frame Rates........................................................................70

2.5 Output Options................................................................................ 71

2.6 Camera Artifacts..............................................................................72

2.6.1 Noise...................................................................................72

2.6.2 Rolling Shutter..................................................................... 74

2.6.3 DSLR Rolling Shutter...........................................................75

2.6.4 Vignetting............................................................................75

2.7 Lens Artifacts...................................................................................76

2.7.1 Lens Distortion....................................................................78

2.7.2 Spherical Aberration............................................................78

2.7.3 Chromatic Aberration...........................................................79

2.7.4 Depth of Field......................................................................79

2.7.5 Veiling Glare.........................................................................80

2.7.6 Lens Flare............................................................................80

2.7.7 Bokeh..................................................................................81

2.7.8 The Swirly Bokeh.................................................................81

2.8 The DIT............................................................................................82

2.8.1 On-Set Support...................................................................82

2.8.2 Data Management...............................................................83

2.8.3 Color Grading......................................................................83

2.8.4 Post-Production Liaison.......................................................83

2.9 Virtual Production............................................................................84

2.9.1 How it Works.......................................................................84

2.9.2 The Promise........................................................................85

2.9.3 The Problems......................................................................86

2.10 What about 35 mm Film?................................................................87

2.10.1 Composition........................................................................87

2.10.2 Frame Rate..........................................................................88

2.10.3 Color Gamut........................................................................88

2.10.4 Grain....................................................................................89

2.10.5 A Softer Look......................................................................89

2.10.6 No Rolling Shutter................................................................90

2.10.7 Color Temperature...............................................................90

2.11 Conclusion.......................................................................................91

Chapter 3 - Storage Space....................................................................... 93

3.1 Image Structure...............................................................................94

3.1.1 Pixels...................................................................................94

3.1.2 Bit Depth.............................................................................95

3.1.3 Channels.............................................................................97

3.1.4 Deep Data...........................................................................98

3.1.5 Metadata...........................................................................100

3.2 Compression Strategies................................................................. 101

3.2.1 Reduced Bit Depth............................................................ 102

3.2.2 Color Subsampling............................................................ 104

3.2.2.1 Luminance and Chrominance............................. 105

3.2.2.2 Subsampling Schemes....................................... 105

3.2.3 Discrete Cosine Transform (DCT)....................................... 107

3.2.4 MPEG................................................................................ 109

3.2.4.1 Spatial Compression........................................... 109

3.2.4.2 Temporal Compression....................................... 110

3.2.4.3 Summary............................................................ 110

3.2.5 Graphics Lossless Compression........................................111

3.2.5.1 RLE Compression................................................111

3.2.5.2 LZW Compression.............................................. 112

3.3 Codecs.......................................................................................... 112

3.3.1 H.264................................................................................ 113

3.3.2 H.265.................................................................................114

3.3.3 JPEG 2000.........................................................................114?

3.3.4 ProRes.............................................................................. 115

3.3.5 DNxHD.............................................................................. 115

3.4 Containers..................................................................................... 116

3.4.1 MOV.................................................................................. 116

3.4.2 MP4................................................................................... 116

3.4.3 AVI......................................................................................117

3.4.4 Summary............................................................................117

3.5 Log Images.....................................................................................117

3.5.1 Why Log?.......................................................................... 118

3.5.2 What is Log Data?............................................................. 120

3.5.3 Data Point Distribution....................................................... 121

3.5.4 How Log Images Are Created............................................ 122

3.5.5 Log for Photography.......................................................... 123

3.6 Cinema Export Options................................................................. 125

3.6.1 Camera RAW..................................................................... 125

3.6.2 Camera Log....................................................................... 126

3.6.3 Compressed Exports........................................................ 126

3.7 Cinema File Formats...................................................................... 127

3.7.1 EXR................................................................................... 128

3.7.2 DPX................................................................................... 129

3.7.3 ProRes.............................................................................. 129

3.7.4 DNxHR.............................................................................. 130

3.7.5 Archival.............................................................................. 130

3.8 Photography Export Options.......................................................... 131

3.8.1 Camera Raw...................................................................... 131

3.8.2 Log Recording (Camera Log)............................................. 131

3.8.3 Compressed Exports........................................................ 132

3.9 Photography File Formats.............................................................. 132

3.9.1 DNG.................................................................................. 133

3.9.2 JPEG................................................................................. 133

3.9.3 PSD................................................................................... 133

3.9.4 PNG.................................................................................. 133

3.9.5 TIFF................................................................................... 133

3.9.6 WebP................................................................................ 134

3.9.7 HEIF.................................................................................. 134

3.9.8 Do Not Use........................................................................ 134

3.10 Conclusion..................................................................................... 135

Chapter 4 - Work Space...........................................................................137

4.1 Color Theory.................................................................................. 138

4.1.1 Additive Color.................................................................... 138

4.1.2 Subtractive Color............................................................... 139

4.2 Color Models................................................................................. 140

4.2.1 RGB.................................................................................. 142

4.2.2 HSL................................................................................... 142

4.2.3 YCbCr............................................................................... 143

4.2.4 CMYK................................................................................ 144

4.3 Color Spaces................................................................................. 145

4.3.1 CIE Chromaticity Diagram.................................................. 146

4.3.2 Primary Chromaticities....................................................... 148

4.3.3 White Points...................................................................... 148

4.3.4 The Transfer Function........................................................ 149

4.3.5 Color Gamuts.................................................................... 151

4.3.6 Pointer's Gamut................................................................. 153

4.3.7 CIEXYZ and CIELAB (CIE L*a*b*)........................................ 153

4.4 Linear vs. Gamma Corrected......................................................... 155

4.4.1 What is Gamma, Exactly?.................................................. 157

4.4.2 Monitor Gamma................................................................. 159

4.4.3 Gamma Correction............................................................ 160

4.4.4 Gamma-Corrected Images................................................ 160

4.4.5 Linear Images.................................................................... 161

4.5 Integer vs. Float............................................................................. 162

4.5.1 Integer............................................................................... 163

4.5.2 Float.................................................................................. 163

4.6 LDR vs. HDR Images..................................................................... 165

4.7 Choosing Your Work Space........................................................... 166

4.7.1 Working in Linear............................................................... 167

4.7.2 Working in Display Space.................................................. 168

4.7.3 Working in ACES............................................................... 169

4.7.4 Working in Log.................................................................. 170

4.7.4.1 Picking the Right Curve....................................... 171

4.7.4.2 Going Negative................................................... 172

4.7.4.3 Limited Dynamic Range...................................... 172

4.8 Photography Work Spaces.............................................................174

4.8.1 sRGB..................................................................................174

4.8.2 Adobe RGB....................................................................... 175

4.8.3 ProPhoto RGB................................................................... 176?

4.8.4 SWOP............................................................................... 176

4.9 Archiving........................................................................................ 178

4.9.1 OpenEXR.......................................................................... 179

4.9.2 DPX................................................................................... 179

4.9.3 Camera Raw...................................................................... 179

4.10 Conclusion..................................................................................... 179

Chapter 5 - Display Space.......................................................................181

5.1 Display Attributes........................................................................... 182

5.1.1 Spectral Emissions............................................................ 182

5.1.2 Color Gamut...................................................................... 183

5.1.3 White Point........................................................................ 184

5.1.4 Transfer Function (Gamma)................................................ 184

5.1.5 Brightness......................................................................... 184

5.1.6 Contrast Ratio................................................................... 185

5.1.7 Bit Depth........................................................................... 186

5.1.8 Frame Rates...................................................................... 187

5.1.9 Refresh Rates.................................................................... 188

5.1.10 Calibration......................................................................... 188

5.1.11 Viewing Surround.............................................................. 189

5.2 SDR vs. HDR................................................................................. 191

5.2.1 Cinema.............................................................................. 192

5.3 HDR Display Formats..................................................................... 192

5.3.1 Hybrid Log Gamma (HLG)................................................. 193

5.3.2 The Perceptual Quantizer (PQ)........................................... 193

5.4 Display Devices.............................................................................. 195

5.4.1 Flat-Panel Display Construction......................................... 195

5.4.2 Workstation Monitors......................................................... 196

5.4.2.1 Specs................................................................. 196

5.4.3 HDTV................................................................................. 197

5.4.3.1 Specs................................................................. 198

5.4.4 Digital Cinema................................................................... 198

5.4.4.1 Specs................................................................. 199

5.5 Coming Soon.................................................................................200

5.5.1 UHDTV..............................................................................200

5.5.1.1 Specs.................................................................202

5.5.2 Digital Cinema 2.0..............................................................203

5.5.2.1 RGB Lasers........................................................203

5.5.2.2 Laser Phosphor..................................................203

5.5.2.3 LED Screens.......................................................204

5.5.2.4 High Frame Rate Movies.....................................204

5.5.2.5 Specs.................................................................205

5.6 Conclusion.....................................................................................205

Chapter 6 - Color Management............................................................ 207

6.1 Color Grading................................................................................208

6.1.1 1D LUTs.............................................................................209

6.1.2 3D LUTs.............................................................................209

6.1.3 Grading Operations........................................................... 210

6.1.4 Range Controls.................................................................. 212

6.1.5 Secondary Color Grading.................................................. 213

6.1.6 Scopes.............................................................................. 215

6.1.6.1 Waveform Monitor............................................... 216

6.1.6.2 Vectorscope........................................................ 217

6.1.6.3 Histogram........................................................... 217

6.1.7 Color Grading in Log......................................................... 218

6.1.8 Using Histograms..............................................................220

6.1.8.1 Color Matching...................................................221

6.1.8.2 Increasing Contrast.............................................221

6.2 Digital Intermediate (DI)..................................................................222

6.2.1 Conforming........................................................................222

6.2.2 The Mastering Process......................................................223

6.2.3 Visual Effects..................................................................... 224

6.2.4 Deliverable File Formats.....................................................225

6.3 ICC Profiles....................................................................................226

6.3.1 How ICC Profiles Work......................................................227

6.3.2 Color Space Conversions..................................................229

6.3.3 Gamut Mapping................................................................229

6.4 Working with Supersized Gamuts.................................................. 231

6.4.1 Viewing Supersized Gamuts.............................................. 231

6.4.2 Remapping Supersized Gamuts........................................232

6.4.2.1 Large to Small Gamuts.......................................232

6.4.2.2 Small to Large Gamuts.......................................233

6.4.3 Tone Mapping....................................................................234

6.4.3.1 Soft Clip LUT......................................................235

6.5 Color Pipelines...............................................................................236

6.5.1 Display Space....................................................................237

6.5.2 Color Managed..................................................................237

6.6 OpenColorIO (OCIO)......................................................................239

6.6.1 Implementation..................................................................239

6.6.2 Color Space Conversions.................................................. 240

6.6.3 Roles................................................................................. 240

6.6.4 Display Transforms............................................................ 241

6.6.5 Look Dev........................................................................... 241

6.6.6 Custom LUTs..................................................................... 241

6.6.7 Color Grading.................................................................... 241

6.6.8 Discipline........................................................................... 242

6.7 ACES Color Management.............................................................. 242

6.7.1 The ACES Workflow.......................................................... 244

6.7.2 ACES Gamuts................................................................... 245

6.7.2.1 ACES 2065-1...................................................... 246

6.7.2.2 ACEScg.............................................................. 247

6.7.2.3 ACEScc.............................................................. 248

6.7.2.4 ACESproxy......................................................... 248

6.7.3 VFX with ACEScg.............................................................. 248

6.7.4 OCIO and ACES................................................................ 249

6.8 Historical Perspective.....................................................................250

6.9 Conclusion..................................................................................... 251

Glossary..................................................................................................... 253

Index............................................................................................................271

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• Produção de filmes: habilidades técnicas e de fundo

Color Science;Visual Effects;Film;TV;Media Effects;Camera;Lens;Color Models;Color Spaces