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TheEffectofGrayBalanceandToneReproductiononConsistentColorAppearance

Nov.28,2016

ElenaFederovskayaandBobChung,RIT

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Introduction

• CMYKimagefiles,whenoutputtoISO15339-2CRPCs,aresaidtohaveconsistentorcommoncolorappearance(CCA)despitetheircolorimetricdifferencesinwhitepointandgamutvolume.• CIEDivision8(ImageTechnology)proposedthestudyof“ConsistentColorAppearance(CCA)”in2016.• Thisprojectexplorestheeffectofgraybalanceandtonereproductionasunderlyingcriteriaofconsistentcolorappearance.

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TheoreticalBasis

• ISO15339-2CRPCs

CRPC CRPC name1 ColdsetNews2 HeatsetNews3 PremUncoated4 SuperCal5 PubCoated6 PremCoated7 Extra Large

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TheoreticalBasis• GamutvolumecomparisonofCRPCsinColorThinkPro3

L* a* b* L* a* b* L* a* b* L* a* b* L* a* b*CRPC1 85 1 5 59 -24 -26 56 48 0 80 -2 60 37 1 4 84,280CRPC2 87 0 3 57 -28 -34 52 58 -2 82 -2 72 30 1 2 151,311∆EabCRPC2 87 0 3 57 -28 -34 52 58 -2 82 -2 72 30 1 2 151,311CRPC3 95 1 -4 60 -26 -44 56 61 -2 89 -3 76 32 1 1 165,764∆EabCRPC3 95 1 -4 60 -26 -44 56 61 -2 89 -3 76 32 1 1 165,764CRPC4 89 0 3 55 -36 -38 47 66 -3 83 -3 83 23 1 2 253,711∆EabCRPC4 89 0 3 55 -36 -38 47 66 -3 83 -3 83 23 1 2 253,711CRPC5 92 0 0 57 -37 -44 48 71 -4 87 -4 88 19 0 1 331,416∆EabCRPC5 92 0 0 57 -37 -44 48 71 -4 87 -4 88 19 0 1 331,416CRPC6 95 1 -4 56 -37 -50 48 75 -4 89 -4 93 16 0 0 389,023∆EabCRPC6 95 1 -4 56 -37 -50 48 75 -4 89 -4 93 16 0 0 389,023CRPC7 97 1 -4 54 -42 -54 47 78 -10 90 -4 103 14 0 0 525,551∆Eab

CRPC

2.0 6.7 6.8 10.0

4.2 6.4 5.2

9.2 9.1

2.0

5.1 6.1 4.0 5.4 3.2

10.7 10.6 5.0 8.1 2.2

6.5 4.2

9.3 12.7 10.3

Paper C100 M100 Y100 K100

3.0 9.2 11.0 12.2 7.3

17%

35%

GamutVolume

GamutVolumeDiff.

80%

10%

53%

31%

5TheoreticalBasis

• Greyreproductionrampspre-definedCMYtripletsareplottedwitha*rampsassolidlinesandb*rampsasdottedlinesinthesamecolorforeachCRPC.• AllCRPCsshowsimilarconvergingpatterns.

!5#

!4#

!3#

!2#

!1#

0#

1#

2#

3#

4#

5#

0# 10# 20# 30# 40# 50# 60# 70# 80# 90# 100#

a*/b*%

%TV%

RPC1_a# RPC1_b# RPC3_a# RPC3_b#

RPC5_a# RPC5_b# RPC7_a# RPC7_b#

!5#

!4#

!3#

!2#

!1#

0#

1#

2#

3#

4#

5#

0# 10# 20# 30# 40# 50# 60# 70# 80# 90# 100#

a*/b*%

%TV%

RPC2_a# RPC2_b# RPC4_a#

RPC4_b# RPC6_a# RPC6_b#

CRPC1,3,5,and7 CRPC2,4,and6

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TheoreticalBasis

• Tonereproductioncurve(TRC)canbeexpressedbyplottingDarkness(100- L*)vs%TVofthecyan.• AllCRPCsshowsimilarhighlight-to-midtoneTRC.

0"

10"

20"

30"

40"

50"

60"

70"

80"

90"

100"

0" 10" 20" 30" 40" 50" 60" 70" 80" 90" 100"

Dk#

%TV#

RPC1_Dk"

RPC3_Dk"

RPC5_Dk"

RPC7_Dk"

0.0"

10.0"

20.0"

30.0"

40.0"

50.0"

60.0"

70.0"

80.0"

0" 10" 20" 30" 40" 50" 60" 70" 80" 90" 100"

Dk#

%TV#

RPC2_Dk"

RPC4_Dk"

RPC6_Dk"

CRPC 1, 3, 5, and 7! CRPC 2, 4, and 6!

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PictorialSimulationofCRPC1~CRPC7(Chung)

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PictorialSimulationofCRPC1~CRPC7(Hutcheson)

81 2 3 4 5 6 7

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SignificanceofISO15339-2CRPCs

• Enabledevicecalibrationand“printingbynumbers”• ThereisalwaysasuitableCRPCtocalibratetheoutputdeviceto.

• Simplifyprepress• Colorimages,separatedforoneoftheCRPCs,canbeprintedinotherCRPCcalibratedprintingconditionsandpreservingconsistentcolorappearance.

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ProblemStatementandResearchQuestion

• Oneproblem• Thereisnorigorousstudythatgraybalanceandtonereproductionareindicativeofconsistentcolorappearance.

• Oneresearchquestion• Howtodeviseapsychometricexperiment,usingstandardCMYKtestimagesandminimumISO15339-2CRPCdatasets,toshowthatgraybalanceandtonereproductionareunderlyingcriteriaofconsistentcolorappearance?

Note:Tostudyconsistentcolorappearance,theminimumnumberofdatasetsis”3”wherethecolordifferencesbetweenthetwoadjacentdatasetsarethesame.

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ExperimentalProcedures1. CRPC5,6,and7arechosenbecausethe95thpercentileCRF∆E00

colorimetricdifferencesbetweenCRPC6andthetwoadjacentCRPCs(outergamut)aresimilar.

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0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8 9 10 11 12

CRF

∆E00

CRPC(1_2)CRPC(2_3)

CRPC(3_4) CRPC(4_5) CRPC(5_6) CRPC(6_7)

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ExperimentalProcedures

2. PreparetestimagesinCRPC5,6,and7conditionstodepictconsistentcolorappearance.

CRPC5CRPC6CRPC7

Scene1

Scene2

Scene3

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ExperimentalProcedures

3. AdjustgraybalanceandtonalreproductionofCRPC6testimages,includingtheIT8.7/4targetandtheP2P25target,suchthat95thpercentile∆E00 betweentheCRPC6andaltered-CRPC6datasetsisthesameasthe95thpercentile∆E00 betweenadjacentCRPCdatasets.

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ExperimentalProcedures4. Conductpsychometricexperimentsbyasking,“whichpictorialimageof

thesamescenelooksmoredifferentthantheotherthree,”duetoalteredgraybalanceandtonereproductioncharacteristics?

CRPC7

CRPC6

CRPC5

CRPC6altered

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ExperimentalProcedures

5. Wecanalsotest“whichpictorialscenelooksmoredifferentthantheotherthreescenes?”duetoalteredgraybalanceandtonereproductioncharacteristicsofaparticularCMYKimage.

Note:We’llneedmorethanthreepictorialscenestoaccomplishthisobjective.