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Color Appearance, Color Order, &
Other Color SystemsMark 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, LightnessBrightness: 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, ChromaSaturation: 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, ChromaINCREASING LIGHTNESS
INCREASING CHROMA
Hue, Lightness, SaturationINCREASING LIGHTNESS
INCREASING SATURATION
Hue, Brilliance, SaturationINCREASING BRILLIANCE
INCREASING SATURATION
INCREASING BRILLIANCE
Hue, Brilliance, SaturationE. 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
L*
a*
b*
light
dark
redgreen
yellow
blue
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 C YA N F I LT E R
Cognition
Colorimetry
CIE XYZ
720380 400 450 500 550 600 650 700
2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Wavelength (nm)
Tris
timul
us V
alue
Z
Y X
Nominal Scaling
Color Matches
No Differences or Appearance
CIELABL*
a*
b*
light
dark
redgreen
yellow
blue
Ratio and Interval Scaling
Color Differences
Approximate Appearance
CIECAM02
Ratio and Interval Scaling
Color Appearance
More Dimensions
Color Systems
Types of Color SystemsColor 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).
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Color Order Systems
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Color Order SystemsSystems 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.
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Munsell
Munsell Book of Color
Munsell Constant-Hue Page
Munsell NotationCricket Software userdict /md known{/CricketAdjust true def}{/CricketAdjust false def}ifelse /mypsb /psb load def /mypse /pse load def/psb {} store /pse {} storecurrentpoint /picOriginY exch def /picOriginX exch defcurrentpoint pop /newWidth exch picOriginX sub defcurrentpoint /newHeight exch picOriginY sub def pop/newXScale newWidth 290 div def/newYScale newHeight 299 div def
Munsell Notation 7.5R 5/10
Hue Value/Chroma
Inspired by Ewald Hering
Realized by Dr Lars Sivik, Prof Gunnar Tonnquist and Dr. Anders Hård,
1997 AIC Judd Award
NCS
Swedish NCS
B
S
R
YG
W
Based on Hering’s Opponency
NCS Hue Circle
NCS Constant-Hue Page
50
Natural Color System (NCS)
G
B
R
YY50RG50Y
B50G R50B
Y90R
s=20
c=70
w
s
c
NCS Notation
20, 70, Y90R Blackness (s), Chromaticness (c), Hue
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Other Systems
PantoneColor Specifications
Proprietary Visual Reference, Not Appearance Scales
RALColor Specifications
Proprietary Visual Reference, Not Appearance Scales
DICColor Specifications
Proprietary Visual Reference, Not Appearance Scales
sRGB, AdobeRGBRGB 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 HuesMunsell : 5 Principal Hues : Based on Thresholds/Differences
NCS : 4 Unique Hues : Based on Appearance
100-100 -80 -60 -40 -20 20 40 60 80
100
-100
-80
-60
-40
-20
20
40
60
80
aR
bR
5Y
5R5G
5B 5P
Individual Differences
Individual Differences
Angelica Dass
CausesGenetics
•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
C I E 2 0 0 6 + I N D I V I D U A L S
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 byMonte Carlo simulation. The test was performed for each of the 10 variables (2 values x 5 matches). Theresults showed the variances were significantly di�erent for 9 variables and were not significantly di�erent for1 variable. The F-test results infer that there are statistical similarities between the model predictions andexperimental data at least for some variables.
It should be pointed out that, regarding the five color matches’ dataset, given that the average intra-observervariability of five color matches was 1.4 (computed from Table 3.5), the di�erence between measured andpredicted 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 SDspredicted by the model are listed. SD units for Stiles & Burch, Asano et al., and Rüfer et al. studiesare rgb-CMFs space (normalized at three primaries’ wavelengths), CIELAB, and Rayleigh Matchunit, respectively.
Validation Datasets Number ofSubjectsSDs SD Ratio
(Pred./Meas.)Meas. Pred.CMFs (Stiles & Burch) 49 0.0374 0.0355 0.95Five Color Matches (Asano et al.) 76 6.49 7.91 1.22Rayleigh Match (Rüfer et 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 theStiles and Burch’s experiment results. The maxima and minima of 49 sets of CMFs for the Stilesand Burch’s experiment participants are superimposed as color-shaded areas. All the CMFs arenormalized to equal area.
To visualize the measured and predicted variability, CMFs measured by Stiles and Burch and CMFs predictedby 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
• Stiles & Burch 49 Observers
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 …
DimensionsLightness - Chroma - Hue
Brightness - Colorfulness - Hue
(Saturation instead of Chroma & Colorfulness??)
Brilliance - Saturation - Hue
(Need at least 5 total, which can be defined by 4.)
ColorimetryCIE XYZ
CIELAB
CIECAM02
(Remember individual variation.)
Color SpecificationPantone, 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