ROY S. BERNS

Chester F. Carlson Center for Imaging Science

Rochester Institute of Technology54 Lomb Memorial Drive

Rochester, New York 14623-5604Berns@cis.rit.edu

http:/www.cis.rit.edu/people/faculty/berns/

ROY S. BERNS

Chester F. Carlson Center for Imaging Science

Rochester Institute of Technology54 Lomb Memorial Drive

Rochester, New York 14623-5604Berns@cis.rit.edu

http:/www.cis.rit.edu/people/faculty/berns/

Challenges forColor Science in

Multimedia Imaging

Challenges forColor Science in

Multimedia Imaging

World Wide Web ChallengeThe Museum of Modern Art , New YorkWorld Wide Web ChallengeThe Museum of Modern Art , New York

Vincent van Gogh, The Starry NightVincent van Gogh, The Starry Night

ImagesImages

TextText

AudioAudio

J. Paul Getty Museum, Los Angeles, CAJ. Paul Getty Museum, Los Angeles, CA

Tone ReproductionTone Reproduction

Typical "Mac" SystemTypical "Mac" System Typical "PC" SystemTypical "PC" System

Color BalanceColor Balance

Typical "Mac" SystemTypical "Mac" System Typical "PC" SystemTypical "PC" System

Tone ReproductionTone Reproduction

Attack on Bunker Hill with the Burning of Charlestown(Unknown artist, circa 1783)Attack on Bunker Hill with the Burning of Charlestown(Unknown artist, circa 1783)

Color Management ChallengeColor Management Challenge

Color Managementvia Profile Connection Space (PCS)Color Managementvia Profile Connection Space (PCS)

drdgdb

CameraColorimetry

XYZ

Color AppearanceModel - CAM

(Scene conditions)

LCH

Inverse CAM(PCS conditions)

L*a*b*0

20

40

60

80

100

L*

-100-50050

100 a*

-100 -50 0 50 100b*

0

20

40

60

80

00

-100-50050

100 a*

drdgdb

LCH

CAM(PCS conditions)

Inverse CAM(Display conditions)

L*a*b*0

20

40

60

80

100

L*

-100-50050

100 a*

-100 -50 0 50 100b*

0

20

40

60

80

00

-100-50050

100 a*

GamutMapping

L*a*b*

Inverse CRTColorimetry

CameraProfile

CRTProflie

PCS

Images as Knowledge ChallengeImages as Knowledge ChallengeSeduction - Color PreferenceIntegrity - Color AccuracyLongevity - Image/Data ArchivesData Mining - Academic Pursuits

Seduction - Color PreferenceIntegrity - Color AccuracyLongevity - Image/Data ArchivesData Mining - Academic Pursuits

Seduction - Georgia O'KeeffeSeduction - Georgia O'Keeffe

+a*+a*

+b*+b*

-b*-b*

-a*-a*

CIELAB Color Gamuts:CRT vs. Photographic PrintCIELAB Color Gamuts:CRT vs. Photographic Print

Gamut "Mapping"Gamut "Mapping"

Color IntegrityTrichromatic AssumptionColor IntegrityTrichromatic Assumption

• Stimuli with the same specification match.• Stimuli that match have the same specification.• Stimuli with the same specification match.• Stimuli that match have the same specification.

X

Y

Z

1

=X

Y

Z

2

11 22

Assume same viewing conditionsAssume same viewing conditions

Multimedia Is Inherently MetamericMultimedia Is Inherently Metameric

7006005004000

20

40

60

80

100

Wavelength (nm)

Rel

ativ

e R

adia

nt P

ower

Color CRT

Caucasian Face in Daylight

The World Is Not Made From: Phosphors and InksThe World Is Not Made From: Phosphors and Inks

Printed PaperPrinted PaperCRT DisplayCRT Display

metsmets

show grum obs met slidesshow grum obs met slides

Inter-observer variance

Inter-observer variance

Intra-observer variance

Intra-observer variance

CRT and Photographic Media Metameric MatchingCRT and Photographic Media Metameric Matching

Alfvin and Fairchild, 1996.Alfvin and Fairchild, 1996.

CIE Standard Deviate ObserverCIE Standard Deviate Observer

0 10

∆ a*

-10

0

10

∆ b*

NimeroffNimeroff

CIE Standard Deviate ObserverCIE Standard Deviate ObserverIntra-ObserverIntra-Observer

Inter-ObserverInter-Observer

Color Measurement1931 Hardy Recording SpectrophotometerColor Measurement1931 Hardy Recording Spectrophotometer

Color MeasurementGretag SpectoScanColor MeasurementGretag SpectoScan

Colorant FormulationColorant Formulation

7006005004000.0

0.1

0.2

0.3

0.4

Standard

Metameric Match

Simple Color Difference

Wavelength (nm)

Re

fle

cta

nce

fa

cto

r

Metameric match has low inherent qualit yMetameric match has low inherent qualit y

Metameric Matches Are Unstable With Changes in LightingMetameric Matches Are Unstable With Changes in Lighting

6806205605004403803800.0

0.1

0.2

0.3

0.4

0.5

Wavelength (nm)R

efle

ctan

ce

Fac

tor

6806205605004403803800.0

0.1

0.2

0.3

0.4

0.5

Wavelength (nm)

Ref

lect

ance

F

acto

r

Two painted surfaces, each colored with different pigments

Two painted surfaces, each colored with different pigments

Daylight IlluminationDaylight Illumination

What a typical observer sees:What a typical observer sees:

Incandescent IlluminationIncandescent Illumination

What a typical observer sees:What a typical observer sees:

The Camera Is Not A HumanThe Camera Is Not A Human

What the camera records under daylight:What the camera records under daylight:

The Camera Is Not A HumanThe Camera Is Not A Human

What the camera records under incandescent:What the camera records under incandescent:

Conventional Imaging Input Devices Are Not Linearly Transformable To Humans

Conventional Imaging Input Devices Are Not Linearly Transformable To Humans

7006506005505004504000.0

0.2

0.4

0.6

0.8

1.0

1.2

nm

Rel

ativ

e se

nsi

tiv

ity

≠≠

Two Issues: Analysis and SynthesisTwo Issues: Analysis and Synthesis

Printing systems are mainly four color, leading to metameric matches

Printing systems are mainly four color, leading to metameric matches

Digital input is notcolorimetricDigital input is notcolorimetric

Photographic input is not colorimetricPhotographic input is not colorimetric

Equivalent to...Equivalent to...

"Colorimeter""Colorimeter" Metameric MatchMetameric Match

The Spectral Challenge: The Spectral Challenge:

7006005004000.0

0.1

0.2

0.3

0.4

Standard

Metameric Match

Simple Color Difference

Wavelength (nm)

Re

fle

cta

nce

fa

cto

r

OriginalOriginal

ReproductionReproduction

A Solution: Multispectral-Based Color ReproductionA Solution: Multispectral-Based Color Reproduction

Image capture

Multi-channel image storage

Spectral-based printing

separation minimizing

metamerism

Multi-ink direct digital

printing

Copyright © 1993, The National Gallery, LondonCopyright © 1993, The National Gallery, London

Spectral reconstruction

Ink selection

Current Research EffortsMy ChallengeCurrent Research EffortsMy Challenge

Multispectral image capture

Spectral models of halftone printing

Statistical representation of paintings

Printing models minimizing metamerism

Color tolerances and spaces

Multispectral image capture

Spectral models of halftone printing

Statistical representation of paintings

Printing models minimizing metamerism

Color tolerances and spaces

Peter BurnsPeter BurnsPh.D. graduate, 1997Ph.D. graduate, 1997

Seven-Channel ColorimeterSeven-Channel Colorimeter

7006005004000.0

0.2

0.4

0.6

0.8

1.0

1.2

Wavelength (nm)

No

rma

lize

d

Tra

nsm

itta

nce

700600500400-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Wavelength (nm)

no

rma

lize

d

cmf*

sou

rce

Thin lines = color matching functionsThick lines = least squares fit

Illuminant A weighted

Matrix TransformationL*a*b*L*a*b*

Define Dataset and Measure a Subset of the ImageDefine Dataset and Measure a Subset of the Image

Spectroradiometry or spectrophotometrySpectroradiometry or spectrophotometry

Describe the Spectral Properties: Principal Component AnalysisDescribe the Spectral Properties: Principal Component Analysis

Seven Filters + Digital CameraSeven Filters + Digital CameraImage sequentially followed by spectral estimationImage sequentially followed by spectral estimation

L*a*b*L*a*b*

Limitation:Digital cameras are low resolutionLimitation:Digital cameras are low resolution

2036x30602036x30603072x40963072x4096

VASARI: Visual Arts System for Archiving and Retreival of Images

VASARI: Visual Arts System for Archiving and Retreival of Images

National Gallery, LondonNational Gallery, London Uffizi Gallery, Florence, ItalyUffizi Gallery, Florence, Italy

Dr. Francisco ImaiDr. Francisco Imai

Postdoctoral FellowPostdoctoral Fellow

Combine:Low Resolution MultichannelHigh Resolution Luminance

Combine:Low Resolution MultichannelHigh Resolution Luminance

7006005004000.0

0.2

0.4

0.6

0.8

1.0

1.2

Wavelength (nm)

No

rma

lize

d

Tra

nsm

itta

nce

Compressing Color Channels Compressing Color Channels

After 16:1After 16:1

BeforeBefore

After 4:1After 4:1

Di-Yuan TzengDi-Yuan Tzeng

Ph.D. Candidate in Imaging SciencePh.D. Candidate in Imaging Science

Statistically Estimate PigmentsStatistically Estimate Pigments

Avg. MI=0.1 ∆E*94

Canonical Correlation AnalysisCanonical Correlation Analysis

The Optimal Ink- S

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700Wavelength

R fl

Warm red

Purple

Reflex blue

Process blue

process black

process yellow

Koichi IinoKoichi IinoVisiting Scientist, ToppanVisiting Scientist, Toppan

Spectral Models of Color PrintingSpectral Models of Color Printing

R a R a R a R a Rc c

n

m m

n

cmyk cmyk

n

w w

n n

λ λλ

λλ

λλ

λλ λ= + + + +( ), , , ,...1 1 1 1

Optical Ink Interaction ModelOptical Ink Interaction Model

q f di i j t jj i

=≠

∏ _ ,( )

Results Estimating MatchprintResults Estimating Matchprint

325 independent colors sampling gamut 325 independent colors sampling gamut

Color Quality MetricsColor Quality MetricsThe Birth of CIELAB, Billmeyer, 1973The Birth of CIELAB, Billmeyer, 1973

City University, LondonCity University, London

WyszeckiRobertson

Ganz

MacAdam

Color Tolerance EquationsColor Tolerance Equations

∆ECH* = ∆L*

kLSL

2

+ ∆C*

kCSC

2

+ ∆H*

kHSH

2

1/2

where

SL = 1.0 SC = 1.0 + 0.045Cab* SH = 1.0 + 0.015Cab

*

9494

Hue Angle DependencyHue Angle Dependency

40030020010000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Luo-RiggRIT-Dupont

Witt

h

Del

ta

Hue

/(1+

0.01

5C*s

td)

0

1

2

3

4

-2 48 98 148 198 248 298

Hue angl e

T5

0

L60c20

L40c35

L40c20 red, L*=42.6, C*=42.6

greenL*=55.2, C*=33.7 blue

L*=35.0, c*=32.8

Previous DataPrevious Data Recent DataRecent Dataabab

Comparisons:CMC, BFD, Current ResultsComparisons:CMC, BFD, Current Results

0

0.5

1

1.5

2

2.5

-2 38 78 118 158 198 238 278 318

hue angle

The

ave

rage

hue

dis

crim

inat

ion

CMC BFDL*=40, C* ab=20 0.39 0.35L*=40, C* ab=35 0.62 0.67L*=60, C* ab=20 0.30 0.29Weightedaverage

0.45 0.45

RMS ∆H*ab errorRMS ∆H*ab error

CMC BFD

Hue LinearityHue LinearityHung and Berns, 1995.Hung and Berns, 1995.

150

50

100

0

-50

-100100500-50-100-150

(a) CIELAB space

(b) CIELUV space

150

50

100

-50

-100

-150

0

150100500-50-100-150 200

(d) Nayatani's model

a*b*

u*

v*

100

50

0

-50

-100

-1500 50 100-50-100

P

T

(c) Hunt's model

100500-50-100-150 150

0

-50

-100

-150

50

100

Myb

Mrg

Gus Braun and Fritz EbnerHue Corrected CIELABGus Braun and Fritz EbnerHue Corrected CIELAB

OriginalOriginalCIELABCIELAB Modified CIELABModified CIELAB

CIE TC 1-47CIE TC 1-47

Hue Angle Correction

Parametric Lightness Function

Evaluate Color Appearance Models

Consider New Color SpaceChroma Compression

Hue Linearity

Hue Angle Correction

Parametric Lightness Function

Evaluate Color Appearance Models

Consider New Color SpaceChroma Compression

Hue Linearity

Spatial + Color DifferenceSpatial + Color Difference

AchromaticRed-Green

Yellow-Blue

∆ ∆ ∆ ∆E

Lk S

Ck S

Hk SL L

ab

C C

ab

H H?*

* * */

=

+

+

2 2 2 1 2

Summary of ChallengesSummary of Challenges

Limitations of Colorimetric Matching

Practical Color Management

Practical Color Appearance Models

Spectral Color Reproduction

Remember the Basics

Limitations of Colorimetric Matching

Practical Color Management

Practical Color Appearance Models

Spectral Color Reproduction

Remember the Basics

Max Saltzman'sThree PrinciplesMax Saltzman'sThree Principles

Color is what is seen: light source, object, observer. Change one, change color.

The sample being judged must be representative of the entire batch of material.

Assess uncertainty in each step of a process.

Color is what is seen: light source, object, observer. Change one, change color.

The sample being judged must be representative of the entire batch of material.

Assess uncertainty in each step of a process.

"Color reproduction is a bloody miracle!"

"Color reproduction is a bloody miracle!"

AcknowledgmentsAcknowledgments

Peter BurnsDi-Yuan TzengGus BraunFrancisco Imai

Peter BurnsDi-Yuan TzengGus BraunFrancisco Imai