1、A Referencenumbe r ISO12645:1998 (E) INTERNATIONAL STANDARD ISO 12645 Firstedition 19981101 GraphictechnologyProcesscontrol Certifiedreferencematerialforopaquearea calibrationoftransmissiondensitometers TechnologiegraphiqueMatrisedeprocdMatrielderfrence certifipourlacalibrationdesdensitomtrestransmi
2、ssionenpourcentage desuperficieopaqueISO12645:1998(E) ISO1998 Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyformorbyan ymeans,electronic ormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromthepublisher. InternationalOrganizat
3、ionforStandardization Casepostale56 CH1211Genve20 Switzerland Internet isoiso.ch PrintedinSwitzerland ii Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughIS
4、Otechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnongovernmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical
5、 Commission(IEC)onallmattersofelectrotechnicalstandardization. DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. InternationalStandardISO12645waspreparedbyT
6、echnicalCommitteeISO/TC130, Graphictechnology . AnnexesAtoEofthisInternationalStandardforinformationonly.ISO ISO12645:1998(E) iii Introduction Inthegraphicarts,themodulationoftransmittanceorreflectanceisoftenachievedbyprintinghalftonesratherthan continuoustones,aswouldbethecaseinphotography. Theproc
7、esscontrolofthegenerationandtransferofhalftonepatternsisessentialtothegraphicartsindustry.For theprocesscontroloftransmissiontypematerialonemonitorsthepercentageofthetotalareathatisvirtually opaque.Measurementsarecarriedoutonwelldefinedhalftonecontrolpatcheswhichcontainregularlyspaced, circularhalft
8、onedots.Themeasuringinstrumentiseitheradensitometeroracolorimeterofthespectrophotometer ortristimulustype.Theopaqueareapercentageisusuallysetequaltotheratiooftherelativetransmittancefactors ofthehalftoneandthatofthesolid.WithdensitometersonecalculatesthetransmittancefactorsfromtheISO standarddiffuse
9、(opal)densities,thecorrespondingexpressionfortheratiohasbeengivenbyMurrayandDavies, seeE.2andequations(1)and(2)ofclause3. Inprinciple,theopaqueareapercentageforpositivepolarityfilmsshouldbeidenticaltothetonevalueasdefinedin thegraphicarts;fornegativepolarityfilmsitshouldbeidenticalto100%minusthetone
10、value.Inreality,however, theremaybeerrorswhichproducesmalldeviationsbetweenthetwoquantities;thereisthusaneedforan independentcheckonthedeterminationofthetonevaluebydensitometersandcolorimeters. Inthegraphicartsprocesschain,particularlyimportantstepsare“imagesetting“,“filmduplication“and “platemaking
11、“.Duringthesesteps,thereisnohighlydiffusivemediumpresentwhichcouldbecomparedtothe opalglassdiffuserofdensitometersaccordingtoISO52E.3.Itwouldthusappearthattheopalglassinstrument isnotthebestsolutionforgraphicartsapplications.However,theopalglassdesignpermitsarelativelysimple construction;suchinstrum
12、entsarewidelyusedinthegraphicartsindustry. Whencalibratingadensitometerwithasteppeddensityreferencematerial(atleasttwosteps),usuallyboththezero pointandtheslopefactorareadjusted.Thelatteristheratioofthedensitydifferencebetweenthestepsasreadby thedensitometerandthedensitydifferenceasreportedbyanation
13、alstandardizinglaboratory.Iftheratiodeviates from1,thebaseofthelogarithmusedforconvertingtransmittancefactorintotransmittancefactordensityisnot10 asrequiredbydefinition.Asaconsequence,thetonevaluescalculatedfromthedensitiesmaydeviatefromthe opaqueareapercentages.Itisimportanttonotethatthe(absolute)I
14、SOstandarddiffusedensitycalibrationofa densitometermaybedependentonthethicknessofthesample.Thesteppeddensityreferencematerialusedfor thedensitycalibrationshouldthereforehavethesamethicknessasthesamplestobemeasured,otherwiseonly relativedensitiescanbemeasured.Formanygraphicartsapplications,however,ab
15、solutedensitymeasurements arenottheissuebutthecontroloftheopaqueareapercentageofhalftonefilm.Thisquantitydeterminesthesize ofimageelements,suchashalftonedotsorlines,producedbytransferstepssuchasfilmduplicationand platemaking.Thedensitometeristhenzeroedontheclearfilmandthedensitiesofahalftoneandasoli
16、dare measured.TheMurrayDaviesformula,E.2andequations(1)and(2)ofclause3,isusedtodeterminetone valuesfromthedensityvalues,seealsoISO126471. Itisknownthattransmissiondensitometersoftheopaltypearesubjecttomultipleobliqueangleinterreflections betweentheopalandthesurfacesclosetoit,seeISO52E.3.Theseinclude
17、thetwosurfacesofthesampleand thoseonthesideoftheinstrumentopposingtheopal.Forsamplesoflowdensity,reflectionsfromallthose surfacesmaycontributetotheeffluxmeasuredatthebackoftheopal.At(absolute)ISOstandarddiffusedensities nearzero,thedensitiesreadbyanopalinstrumentarethusslightlylowerthanthoseofadiffu
18、sespheretype instrument;0,03isatypicaldifference.Thiseffecthastobetakenintoaccountiftransmissiondensitiesor reflectancefactorsreadbyinstrumentsofdifferentdesignarecompared.Forsamplesofhigherdensities,the reflectionsfromallsurfacesbutthesurfacenexttotheopalareeffectivelysuppressed.Duringthemeasuremen
19、tof ahalftonepattern,thelatterinfluencestheinterreflectioneffectintwoways:Theimageelementsmayhavea reflectancedifferentfromthefilmbase,theyalsotendtoattenuatereflectionsfromsurfacesfurtherremovedfrom theopal.Therefore,thetonevaluesdeterminedfromdensitiesmeasuredwithanopalinstrumentmaydifferfrom thea
20、ctualopaqueareapercentageofthesamplewhichcanbedeterminedbymicroscopicmeasurementorbya spheretypeinstrument(whichdoesnotshowtheinterreflectioneffect). ISO126471specifiesthattransmissiondensitiesshallbemeasuredbyinstrumentscomplyingtoISO52,thus therecanbenoambiguitywhenquoting(absolute)ISOstandarddiff
21、usedensitiessuchasclearfilmdensities.ISO12645:1998(E) ISO iv Theinterreflectioneffectcanbeartificiallyattenuatediftheopaliskeptatadistanceof,say,25mmfromthe measuredobject.Anothermethodistoplaceaneutralfilterwithadensityofatleast0,3betweentheopalandthe sample.Thefiltertendstoattenuatethelightcomingb
22、ackfromtheopaltowardsthesampleandalsothe reflections. Theinterreflectioneffectmayproduceadiscrepancyoftypically3%betweenthetonevalueofahalftoneas determinedwithatransmissiondensitometeroftheopaltypeandtheopaqueareapercentageasdeterminedfrom independentmeasurementsofthedotpattern.Thediscrepancycannot
23、becircumventedbyproperzeroingor adjustmentoftheslopefactoroftheinstrument,itdependsonthemagnitudeoftheopaqueareapercentage.Thus thereisaneedforanindependentcheckonthetonevaluedeterminationbyatransmissiondensitometerand,if necessary,theestablishmentofatablethatconvertstonevaluesintoopaqueareapercenta
24、ges.ThisInternational Standardspecifiesrequirementsfortwotypesofreferencematerialsthatprovidehalftonecontrolpatcheswithdot patternsofaccuratelydefineddimensionsthatmayserveas“Certifiedreferencematerials“(CRM)ifthe requirementsofISO15790 1) arealsofulfilled. Referencematerialsmaybeproducedfromhalfton
25、efilmmaterialorathinglassslabwithachromiumdeposit.The lattersadvantagesareaverysmallfringewidth,awavelengthindependentattenuationandagooduniformityof opaqueareapercentageoverthecontrolpatch.Thethickness,thescatteringpropertiesandthewavelength dependenceofthetransmissiondensitydifferfromthoseofgraphi
26、cartsfilmmaterial.Itmightthusbesuspected thatthisinvalidatestheuseofsuchareferencematerialasastandard.Ithasbeenshown,however,thatthickness changesoflessthan1mmshiftonlythezeropointofadensitometer,thusthedensitometricopaquearea percentagecalculationisnotaffected.Othertestseriesshowedthatinterposingfi
27、lmsofvaryingscattering propertiesbetweenthechromium/glassreferencematerialandtheopaldidnotaffecttheopaqueareapercentage determination,withinthemeasurementaccuracy.Theabsenceofawavelengthdependencecanberegardedasan asset:Sincethewavelengthdependenciesofgraphicartsfilmsdiffermuchfromeachother,thereisn
28、oestablished dependencethatcouldbeusedforsuchareferencematerial. _ 1)SeeinformativeannexE .INTERNATIONALSTANDARD ISO ISO12645:1998(E) 1 GraphictechnologyProcesscontrolCertifiedreference materialforopaqueareacalibrationoftransmissiondensitometers 1Scope ThisInternationalStandarddefinesrequirementsfor
29、ahalftonecertifiedreferencematerialwhichmaybeusedfor theopaqueareapercentagecalibrationoftransmissiondensitometersorcolorimetersforuseinthegraphicarts. ThisInternationalStandardisnotapplicabletothecalibrationoftransmissiondensitometersintermsofISO standarddiffusedensity. NOTE Testmethodsfordetermini
30、ngtheopaqueareapercentagearegivenintheinformativeannexA. 2Normative reference Thefollowingnormativedocumentcontainsprovisionswhich,throughreferenceinthistext,constituteprovisionsof thisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthese publicationsdonotapply.How
31、ever,partiestoagreementsbasedonthisInternationalStandardareencouragedto investigatethepossibilityofapplyingthemostrecenteditionofthenormativedocumentindicatedbelow.For undatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIEC maintainregistersofcurrentlyvalidIntern
32、ationalStandards. ISO126471:1996, GraphictechnologyProcesscontrolforthemanufactureofhalftonecolourseparations, proofandproductionprintsPart1:Parametersandmeasurementmethods. 3Definitions ForthepurposesofthisInternationalStandard,thedefinitionsgiveninCIE17.4andthefollowingapply.Theyare giveninalphabe
33、ticalorder. NOTE Forquantities,thepreferredunitisgiventogetherwiththedefinition.Bydefinition,theunitofformerlysocalled “dimensionlessquantities”is1. 3.1 controlpatch areaproducedforcontrolandmeasurementpurposes ISO126471 3.2 coredensity transmissiondensityinthecentreofanisolatedopaqueimageelementsuc
34、hasahalftonedotorline Unit:1 ISO126471 3.3 fringewidth (ofanisolatedopaqueimageelement) averagedistancebetweenthedensitycontourlinescorrespondingto10%and90%oftheminimumcoredensity specifiedfortheprintingprocessunderconsideration Unit:m ISO126471ISO12645:1998(E) ISO 2 3.4 opaqueareapercentage P perce
35、ntageoftotalareathatisnearlyopaquetoradiationinthewavelengthrangeofinterest 3.5 polarity (ofatransmissionobject) positiveifclearandsolidareasontheobjectcorrespondtounprintedandsolidareasontheprint,respectively. Negativeifclearandsolidareasontheobjectcorrespondtosolidandunprintedareasontheprint,respe
36、ctively 3.6 screenruling screenfrequency f numberofimageelements,suchasdotsorlines,perlengthinthedirectionwhichproducesthelargestnumber Unit:cm -1 ISO126471 3.7 screenwidth reciprocalofscreenfrequency Unit:cm ISO126471 3.8 tonevalue dotarea(onatransmissionobjectofpositivepolarity) A percentagecalcul
37、atedfromtheformula: A DD DD =- - - - - 100 100 % 11 0 11 0 () () t0 s0 .(1) where D 0 isthetransmissiondensityoftheclearsubstrate; D s isthetransmissiondensityofthesolid; D t isthetransmissiondensityofthehalftone. ISO126471 NOTE Alsoknownasfilmprintingdotarea. 3.9 tonevalue dotarea(onahalftoneobject
38、ofnegativepolarity) A percentagecalculatedfromtheformula: A DD DD =- - - - - 100 100 % 11 0 11 0 () () t0 s0 .(2) where D 0 isthetransmissiondensityoftheclearsubstrate; D s isthetransmissiondensityofthesolid; D t isthetransmissiondensityofthehalftone. ISO126471 NOTE Alsoknownasfilmprintingdotarea.IS
39、O ISO12645:1998(E) 3 4Requirements 4.1Materials Thesubstrateshallconsistofaclearmaterialwithapatternofopaquehalftonedotsononeside.Atnormal incidencethe(absolute)reflectancefactor(frontandsecondsurface)shallnotbehigherthan0,05. 4.2Thickness Thenominalthicknessshallbeselectedfromtherange0,1mmto0,8mm.T
40、hemeasuredthicknessshallnotvary bymorethan0,01mmacrossthecertifiedreferencematerial. 4.3Halftone pattern Thecertifiedreferencematerialshallshowcontrolpatcheswhoseminimumsizesshallbegreaterthan5mmin diameterandshouldnotbesmallerthan10mmindiameter.Theshapeofthehalftonedotsshallbenominally circular.The
41、screenrulingshallbeselectedfromtherange50cm -1 to70cm -1 ,itshallbeconstantoverthe certifiedreferencematerial. Thecertifiedreferencematerialshallshowcontrolpatcheswithatleastthefollowingopaqueareapercentages: circularopaquehalftonedots:20%or25%,50%; circularclearhalftonedots:75%or80%. Inaddition,con
42、trolpatchesshowing0%and100%(solid)shallbeprovided.Controlpatcheswith2%and98% shouldbeprovidedaswell. Deviationsof1%(absolute)shallbepermittedforthechoiceofthenominalopaqueareapercentage.Allcontrol patchesshouldbelabelledwiththenominalopaqueareapercentages. Thefringewidthofthehalftonedotpattern(seetheinformativeannexD)shouldnotbegreaterthan2mas determinedbytheapparatusdescribedinISO126471.TheISOStatusA(blue)andtheISOvisualstandard diffusetransmissiondensityofthesolid(opaque)contro
