quantitative testing of color appearance models using the … · 1999. 10. 5. · david r. wyble,...

David R. Wyble, Mark D. Fairchild RIT/MCSL ISCC Baltimore, October 3, 1998 p.1

Quantitative Testing of ColorAppearance Models Using theMunsell Renotation DataDavid R. Wyble, [email protected]

Mark D. Fairchild, [email protected]

RIT Munsell Color Science LaboratoryChester F. Carlson Center for Imaging Science54 Lomb Memorial DriveRochester NY 14623-5604


Outline

u Introduction

u Munsell Renotation Data

u Color Appearance Models

u Color Appearance Metrics

u Color Appearance Model Performance

u Applications

u Conclusion


Testing Appearance Models

u Why evaluate models?● There are so many!

u Do we need one model?● Color management demands this

u This work is the first application of Munselldata to this set of color appearance models


Munsell Renotation Data

u Chromaticities used are as published byNewhall, et al, JOSA 1943

u Extracted real colors from data provided byD. Rich and R. Berns

u Illuminant C tristimulus values are inputdata for all models


Model Evaluation

u Models were evaluated only for lightness,chroma, and hue attributes

u All metrics are based on these threeappearance attributes

u Metrics focus on the particular property ofthe Munsell Renotation Data, wherebyappearance attributes are constant alongeach dimension.


Appearance Models Used Here

u CIELAB (CIE, 1976)

u RLAB (Fairchild, 1994)

u Hunt94 (Hunt, 1994)

u Nay95 (Nayatani, et al, 1995)


Appearance Models Used Here

u LLAB (Luo, et al, 1996)

u CIECAM97s (CIE TC1-34, 1997)

u ZLAB (Fairchild, 1997)

u IPT (Ebner, et al, 1998)

Excel and IDL code can be found at:www.cis.rit.edu/people/faculty/fairchild/CAM.html


Appearance Models Conditions

u Recommended Munsell viewing conditions

u CIE Illuminant C, 1931 2° observer

u Where applicable, fully discount illuminant

u Absolute white luminance = 400 cd/m2

u Correlated color temperature = 6774°K


Goals and Expectations

u Goal here is to evaluate the uniformity ofthese models with respect to the constanthue, chroma, and lightness properties of theMunsell Renotation Data

u We expect CIELAB and RLAB to performvery well


Appearance Model Metrics

u Chroma Circularity

u Chroma Linearity

u Hue Linearity

u Hue Spacing

u Lightness Linearity


Chroma Circularity Description

Input data arecircles of constantMunsell chroma



Chromas for each model are normalized tothat model’s chroma at value=5, chroma=6:

C normalized =Cmodel

C model,6

CMunsell,6



Normalized Model Chroma vs Munsell Hue

Model Chroma

Average Chroma

B/Y

R/G


Chroma Circularity Results

4.0

5.0

6.0

7.0

8.0

9.0

10RP 10R 10YR 10Y 10GY 10G 10BG 10B 10PB 10P

Munsell Hue

MunsellChroma

CIELABRLABZLABCIECAM97sHunt94Nay95LLABIPT


ZLAB

RLABNay95

Hunt94CIECAM97s

CIELAB

LLABIPT

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Chroma Circularity Summary

RMS difference between Munsell and normalized modelchroma for four Munsell value/chroma combinations.

Ave

rage

Chr

oma

Erro

r(n

orm

aliz

ed M

unse

ll ch

rom

a un

its)


Chroma Linearity Description

Input data arelines of constantMunsell chroma

and hue


Chroma Linearity Description

u Chromas for each model are normalized tothat model’s chroma at value=5, chroma=6

u RMS difference between normalizedchromas and their normalized averages


21

2

3

4

5

6

7

8

9

Normalized chroma(Munsell chroma units)

5R

Chroma Linearity Results

CIELAB chroma lines forMunsell chroma=2,

hue=5R (red)

Cnormalized,2 =Cmodel ,2

C m o d e l , 6

CMunsell,6

Mun

sell

Val

ue


2 4 6 824681

2

3

4

5

6

7

8

9

Normalized chroma (Munsell chroma units)

CIELAB

CIECAM97s

5R5BG


Constant chroma lines for red/green slice of Munsell space

Mun

sell

Val

ue


2 4 6 824681

2

3

4

5

6

7

8

9

Normalized chroma (Munsell chroma units)

CIELAB

CIECAM97s

10BP10Y


Constant chroma lines for blue/yellow slice of Munsell space

Mun

sell

Val

ue


Chroma Linearity Summary

Chroma error from average normalized chroma

IPTRLAB

LLAB ZLABNay95

Hunt94

CIECAM97sCIELAB

0.0

0.2

0.4

0.6

0.8

1.0

1.2A

vera

ge

Chr

oma

Erro

r(n

orm

aliz

ed M

unse

ll ch

rom

a un

its)


Hue Linearity Description

Input data arelines of constantMunsell hue and

value


Hue Linearity Description

u Report RMS and max difference between predicted hueand hue at Munsell chroma=6

Predicted Color

Hue at chroma=6

Hue Error

R/G

B/Y


Hue Linearity Results

RMS difference from hue at chroma=6.

0

1

2

3

4

5

6

7

8

10RP 10R 10YR 10Y 10GY 10G 10BG 10B 10PB 10P

Munsell hue

CIELAB RLAB

ZLAB CIECAM97s

Hunt94 Nay95

LLAB IPT

Hue

Err

or (

°)


Hue Linearity Results

Maximum difference from hue at chroma=6.

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

10RP 10R 10YR 10Y 10GY 10G 10BG 10B 10PB 10PMunsell hue

CIELAB RLABZLAB CIECAM97sHunt94 Nay95LLAB IPT

Max

imum

hue

err

or (

°)


Hue Linearity Summary

Hue error at Munsell value=5

Nay95

CIELAB LLABZLAB RLAB IPT

Hunt94

CIECAM97s

0.0

0.5

1.0

1.5

2.0

2.5A

vera

ge

Hue

Err

or (

°)


Hue Spacing Description

Input data arecircles of constantMunsell chroma


Hue Spacing Description

u Reported as RMS difference betweenpredicted hue and ideal spacing

u Ideal hue spacing is 360°/40 hues = 9°


Hue Spacing Results

4

6

8

10

12

14

16

18

20

10RP 10R 10YR 10Y 10GY 10G 10BG 10B 10PB 10PMunsell Hue

CIELABRLABZLABCIECAM97sHunt94Nay95LLABIPT

Hue

Spa

cing

(°)

Distance between hue lines at Munsell value=5, chroma=6


Nay95 IPT

ZLAB LLAB CIELAB RLAB

Hunt94CIECAM97s

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Hue Spacing Summary

Ave

rage

Hue

Spa

cing

Err

or (

°)

Average hue spacing error at Munsell value=5, chroma=6


Lightness Linearity Description

u Input data are Munsell value scale (neutrals)

u Plotted as lightness vs Munsell Value

u Linearity reported as distance betweentranslated, normalized data and Munsellvalue


Lightness Linearity Description

-200

20406080

100120

0 2 4 6 8 10Munsell Value

0

20

40

60

80

100

120


0

2

4

6

8

10


Lightness translation and normalization.

Raw Lightness Translated Raw Lightness Normalized Lightness


Lightness Linearity Results

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10

Munsell Value

CIELAB

CIECAM97s

Normalized lightness for CIELAB and CIECAM97s

Nor

mal

ized

lig

htne

ss


Lightness Linearity Summary

Average difference between normalized lightness and Munsell value

ZLAB

LLABHunt94

RLAB IPT

Nay95

CIELAB

CIECAM97s

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35N

orm

aliz

ed

light

ness

(M

unse

ll va

lue

unit

s)


Model Performance Summary

u Models excel at different metrics

u Currently no appropriate method toquantitatively rank model performance● It would be too deceptive

● In many ways, it would be incorrect

u If a statistical comparison can be devisedwhich uses all the metrics described here, itwill appear in future work


The Old Way

My Model

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

-12 -8 -4 0 4 8 12

CIELAB

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

-12 -8 -4 0 4 8 12


The New: CIECAM97s

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

-12 -8 -4 0 4 8 12

The past and the future?

The Old: CIELAB

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

-12 -8 -4 0 4 8 12


Possible Applications

u Model designers can clearly see shortfalls

u These techniques can be used to help selecta model for a specific purpose

u Can we do another correction of Munsellspace?


Conclusions

u Eight modern color appearance models

u Evaluation using the Munsell Renotationdata as visually-uniform input colors

u Models evaluated for constant lightness,chroma, and hue response

u Comparisons were made for modeluniformity with respect to the MunsellRenotation Data


Conclusions

u No clear winners or losers, but rather cleardistinctions between predictive abilities ofthe various models for various metrics

u No claim is being made as to the ability tocompare these results to other colorappearance model studies● Cross-media reproduction

● Color difference comparisons

quantitative testing of color appearance models using the … · 1999. 10. 5. · david r. wyble,...

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