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

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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