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Munsell 2018 Spaces Tutorial

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Color Appearance, Color Order, & Other Color Systems Mark Fairchild Rochester Institute of Technology Integrated Sciences Academy Program of Color Science / Munsell Color Science Laboratory ISCC/AIC Munsell 2018 — Boston RIT ISA PoCS / MCSL Color Terms Color Definition Color is an attribute of visual sensation … Hue Attribute of a visual sensation according to which an area appears to be similar to one of the perceived colors, red, yellow, green, and blue, or to a combination of two of them. Brightness, Lightness Brightness: Attribute of a 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 to be white or highly transmitting. Colorfulness Attribute of a visual sensation according to which the perceived color of an area appears to be more or less chromatic. Saturation, Chroma Saturation: Colorfulness, chromaticness, of an area judged in proportion to its brightness. Chroma: Colorfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting. Hue, Lightness, Chroma INCREASING LIGHTNESS INCREASING CHROMA Hue, Lightness, Saturation INCREASING LIGHTNESS INCREASING SATURATION Hue, Brilliance, Saturation INCREASING BRILLIANCE INCREASING BRILLIANCE INCREASING SATURATION Hue, Brilliance, Saturation E. Hering: Zur Lehre vom Lichtsinne (1878) A. Pope: Tone Relations in Painting (1922) R. Evans: The Perception of Color (1974) Scandinavian Colour Institute: Natural Color System (1978) M. Fairchild & R. Heckaman: Deriving Appearance Scales (2012) Color Perception Color Science The Eye The Retina light L* yellow b* green red a* blue dark Skin Color Variations One Person — Hemoglobin Level and Oxygenation (Melanin Fixed) Mean Color Background Credit — Chris Thorstenson (RIT & UR) Simultaneous Contrast Simultaneous Contrast Simultaneous Contrast White’s The Brain Chromatic Adaptation A CYAN FILTER Cognition Colorimetry CIE XYZ 2 1.8 Z 1.6 1.4 1.2 Y X 1 0.8 Tristimulus Value Tristimulus 0.6 0.4 0.2 0 380 400 450 500 550 600 650 700 720 Wavelength (nm) Nominal Scaling Color Matches No Differences or Appearance CIELAB light L* yellow b* Ratio and Interval Scaling green red Color Differences a* Approximate Appearance blue dark CIECAM02 Ratio and Interval Scaling Color Appearance More Dimensions Color Systems Types of Color Systems Color Naming Systems: Color is defined and specified according to some, essentially arbitrary, naming system (e.g., Pantone, Trumatch, Paint Color Cards). Color Mixing Systems: Color is defined according to the properties of a given system (e.g., RGB, CMYK, HSV, DIN, XYZ, etc.) Hybrid Systems: Color is defined by a combination of systems (e.g., appearance and additive mixing in Colorcurve). Color Appearance Systems: Color is defined according to various appearance attributes (e.g., Hue, Value, Chroma in Munsell, Hue, Blackness, Chromaticness in NCS, Color differences in OSA UCS). 39 Color Order Systems 40 Color Order Systems Systems that define color appearance according to some orderly arrangement to facilitate the naming and communication of colors (among other applications). Often the systems define colors using perceptual variables. Such systems are typically embodied with atlases of color samples rather than through mathematical relationships to colorimetric coordinates. Color Appearance Systems The Munsell system (Munsell Book of Color) and Swedish Natural Color System (NCS) provide two important examples of systems defined by color appearance. Thus their scales, while not defined mathematically can be used to develop and test color appearance models. 42 Munsell Munsell Book of Color Munsell Constant-Hue Page Munsell Notation Cricket/mypsb/newYScale/psbcurrentpointuserdict/newXScale {} Software store/psb /md newHeight loadnewWidth/picOriginYpop/newHeightknown{/CricketAdjust/pse /newWidth def{} store/mypse 290299 exchexch div div exch/pse picOriginYdef defdef load picOriginX/picOriginX true def def}{/CricketAdjust sub subdef exch popdef def false def}ifelse Munsell Notation 7.5R 5/10 Hue Value/Chroma NCS Inspired by Ewald Hering Realized by Dr Lars Sivik, Prof Gunnar Tonnquist and Dr. Anders Hård, 1997 AIC Judd Award Swedish NCS W G Y B R S Based on Hering’s Opponency NCS Hue Circle NCS Constant-Hue Page 50 Natural Color System (NCS) Y w G50Y Y50R c G Y90R R s=20 s B50G R50B B c=70 NCS Notation 20, 70, Y90R Blackness (s), Chromaticness (c), Hue 51 Other Systems Pantone Color Specifications Proprietary Visual Reference, Not Appearance Scales RAL Color Specifications Proprietary Visual Reference, Not Appearance Scales DIC Color Specifications Proprietary Visual Reference, Not Appearance Scales sRGB, AdobeRGB RGB Primaries Specified Tone Transfer Specified XYZ-to-RGB Defined Rec.709, Rec.2020 RGB, HSL, HSV, CMYK Device Dependent Spaces RGB/CMYK Not Defined Categories of Systems (1) Systems Related to Colorimetry (e.g., XYZ) or Not (2) Systems Based on Color Appearance or Not Munsell & NCS: (1) Yes (2) Yes sRGB & Rec.2020: (1) Yes (2) No Pantone, RAL, Paints: (1) No** (2) No **Proprietary Principal/Unique Hues 100 5Y Munsell : 5 Principal Hues : 80 Based on Thresholds/Differences 60 5R NCS : 5G 40 4 Unique Hues : 20 Based on Appearance R b -100 -80 -60 -40 -20 20 40 60 80 100 -20 -40 -60 -80 5B 5P -100 aR Individual Differences Individual Differences Angelica Dass Causes Genetics •Different Pigments (Color Blind in Extreme) •Different Pigment Density •Cone Morphology •Eye “Color” Diet, Lifestyle, Environment, Age •Macular Pigment Density •Lens Density Psychology, Cognition •Knowledge of Conditions •“Set” of Judgments •Available Vocabulary color matches’ dataset, one sample was the adjusted a* and b* values of five color matches for 76 observers, and the other sample was the simulated a* and b* values of five color matches for 1000 CMFs generated by Monte Carlo simulation. The test was performed for each of the 10 variables (2 values x 5 matches). The results showed the variances were significantly different for 9 variables and were not significantly different for 1 variable. The F-test results infer that there are statistical similarities between the model predictions and experimental data at least for some variables. It should be pointed out that, regarding the five color matches’ dataset, given that the average intra-observer variability of five color matches was 1.4 (computed from Table 3.5), the difference between measured and predicted SDs (1.42 CIELAB unit) in Table 3.7 would be perceptually small. Tab. 3.7 – Validation results of the proposed vision model. SDs measured (obtained) by each study and SDs predicted by the model are listed. SD units for Stiles & Burch, Asano et al., and Rüfer et al. studies are rgb-CMFs space (normalized at three primaries’ wavelengths), CIELAB, and Rayleigh Match unit, respectively. Number of SDs SD Ratio Validation Datasets CIE 2006 + INDIVIDUALSSubjects Meas. Pred. (Pred./Meas.) CMFs (Stiles & Burch) 49 0.0374 0.0355 0.95 Five Color Matches (Asano et al.) 76 6.49 7.91 1.22 • Stiles Rayleigh& Burch Match (Rüfer 49 et Observers al.) 113 2.7 3.1 1.15 Fig. 3.12 – 49 sets of rgb-CMFs generated by the proposed observer model (gray lines) aiming to predict the Stiles and Burch’s experiment results. The maxima and minima of 49 sets of CMFs for the Stiles and Burch’s experiment participants are superimposed as color-shaded areas. All the CMFs are normalized to equal area. To visualize the measured and predicted variability, CMFs measured by Stiles and Burch and CMFs predicted by the proposed vision model were compared in Figure 3.12. Gray lines represent 49 sets of rgb-CMFs 3.2 Individual Colorimetric Observer Model 43 Color Rendering Animal Vision Animal Vision Birds Kestrel Bird Vision Bees Bee Color Vision Dashed - Honey Solid - Bumble Bee Color Vision Humans Honey Bees Goldfish Goldfish Color Vision Mantis Shrimp Complexity Final Thoughts … Dimensions Lightness - Chroma - Hue Brightness - Colorfulness - Hue (Saturation instead of Chroma & Colorfulness??) Brilliance - Saturation - Hue (Need at least 5 total, which can be defined by 4.) Colorimetry CIE XYZ CIELAB CIECAM02 (Remember individual variation.) Color Specification Pantone, RAL, etc. sRGB, Rec.709, Rec.2020, Dolby ICtCp (All could be replaced by colorimetry, but they are convenient and helpful.) Color Order Munsell NCS (Perhaps could be replaced by a CAM one day.) Questions.
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