Imatest史上最详细教程(2)

Imatest史上最详细教程2009ImatestLLCImatestDocumentation1of451ImatestDocumentationImageQualityAnoverviewofthekeyimagequalityfactorsandhowtheyaremeasuredbyImatestSharpness-Whatisitandhowisitmeasured?Introduction-TheSlanted-edgetest-Calculationdetails-Results-InterpretingMTF50SQF-SubjectiveQualityFactorIntroduction-SQFandMTF-MeaningofSQF-MeasuringSQF-TheSQFequation-CSF-LinksNoiseinphotographicimagesIntroduction-Appearance-Noisemeasurements-Noisesummary-F-stopnoise-Themathematicsofnoise-LinksSharpening-WhystandardizedsharpeningisneededforcomparingcamerasStandardizedsharpening-ExamplesSharpnesscomparisons-forseveraldigitalcamerasIntroduction-Explanationofresults-Tablesofresults-InterpretationofMTF-Someobservations-LinksChromaticAberration-AKAColorfringingIntroduction-Measurement-DemosaicingVeilingglare(Lensflare)Introduction-Target-Measurement-Results-ISO9358ColorcorrectionmatrixIntroduction-Math-MultichartsISOSensitivityandExposureIndexIntroduction-Modules-Equations-RAWfiles-RelateddocumentsShannoninformationcapacity-informationthatcanpassthroughachannelwithouterrorMeaning-Results-SummaryBlurunits,MTF,andDXOAnalyzer'sBxUTheImatestTestLab-HowtobuildatestinglabIntroduction-Hardware-Lighting-Easel-Lightmeasurement-Tripod-Clamps-Puttingittogether-Targets-Aligningtarget&cameraImatestInstructions--GeneralInstallation-andgettingstartedInstall-Purchase-Register-Offlineregistration-FilesUsingImatestRunningImatest-multi_read-RAWfiles-Othercontrols-Pulldownmenus-Figures-.CSVandXMLoutput-UseofImatestRAWfilesIntroduction-UsingRAWfiles-BayerRAW-dcrawdemosaicing-Rawviewutility-GeneralizedReadRawTheImatestTestLab-HowtobuildatestinglabIntroduction-Hardware-Lighting-Easel-Lightmeasurement-Tripod-Clamps-Puttingittogether-Targets-Aligningtarget&cameraTroubleshooting-WhattodowhenImatestdoesn'tworkInstallationproblems-Problemsafterinstall-MissingDLLs-Runtimeproblems-INIfiles-Command(DOS)window-Diagnosticsruns-PathconflictsImatestInstructions--SharpnessmodulesUsingSFRPart1-SettingupandphotographingSFRtargetsSlanted-edgetest-Printchart-Lighting-Distance-Exposure-Tips-QualityandDistanceUsingSFRPart2-RunningImatestSFRImagefile-ROI-Additionalinput-Equations-Gamma-Warnings-Saving-Repeatedruns-ExcelCSVoutputImatestSFRLCDtargetScreenPatternsmodule-WebpatternSFRresults:MTF(Sharpness)plotSFRresults:-ChromaticAberration,Noise,andShannoncapacityplotSFRresults:MultipleROI(RegionofInterest)plot2DSummaryplot-1DSummaryplot-CSVOutputfile-Summaryexplanation-ExcelplotsUsingSFRplusPart1-TheSFRpluschart:featuresandhowtophotographitSlanted-edgetest-Advantages-Obtainchart-Printchart-Lighting-Distance-Exposure-Tips-QualityandDistanceUsingSFRplusPart2-RunningImatestSFRplusRunningSFRplus-Rescharts-SFRplussettingswindows-Parameters&setupwindow-Settings&optionswindow-Gamma-Warnings-SFRplussummaryImatestDocumentation2of451UsingSFRplusPart3-ImatestSFRplusresultsSFRplusresults-Saving-Repeatedruns-Excel.CSV(CommaSeparatedValues)outputUsingRescharts-Analysisofresolution-relatedchartsIntroduction-Gettingstarted-TheReschartswindow-Reschartsmodules-Slanted-edgeSFR-Logfrequency(simple)-Logfrequency-contrastLogFrequency-Analysisoflogfrequency-varyingchartsIntroduction-Photographing,running-Colormoire-Output-Pattern-MTF-Comparisons-Calculationdetails-Nyquist,aliasingLogF-Contrast-AnalysisofchartsthatvaryinlogfrequencyandcontrastIntroduction-Creating,printing-Photographing,running-Output-Pattern-MTF-MTF/contrastcontours-MTFnnStarChart-AnalysisoftheSiemensstarchartIntroduction-Creating,photographing,running-Output-MTF-MTFnn,MTFnnP-MTFcontours-EquationsMTFCompare-CompareMTFsofdifferentcamerasandlensesIntroduction-InstructionsBatchview-PostprocessorforviewingsummariesofSFR,SFRplusresultsIntroduction-Preparation-InstructionsHowtoTestLenseswithSFRplusIntroduction-Testchart-Photograph-RunSFRplus-ReschartsSFRplus-SFRplussettings-Interprettheresults-Batches-ChecklistHowtoTestLenseswithSFR-(oldpage:ImatestSFRplusrecommended)Introduction-Testtarget-Photograph-RunSFR-Interpret-ChecklistImatestInstructions--Tone,color,andspatialmodulesUsingStepchartPhotographingthechart-RunningStepchart-Output-Saving-Dynamicrange-AlgorithmStepchart:AppliedImageandISOchartsPhotographingchart-Instructions-PatchorderDynamicRange-CalculateDynamicRangefromseveralStepchartimagesIntroduction-Operation-Results-DynamicRangebkgndUsingColorcheckWhatColorcheckdoes-Colorcheckercolors-Photographingtarget-Photographingtarget-Colorcheckerreferencesources-Output-Saving-LinksColorcheckAppendix-AlgorithmsandreferenceformulasColorerrorformulas-Algorithm-GrayscaleandexposureUsingMulticharts-InteractiveanalysisofseveraltestchartsIntroduction-Gettingstarted-Referencefiles-TheMultichartswindow-DisplaysandoptionsMultichartsSpecialCharts-Additionalcharts,includingcirclesarrangedonasquareInstructions-Patchnumbering-ExamplesColorcorrectionmatrixIntroduction-Math-MultichartsUsingUniformity(LightFalloff)-Measureslightfalloff(lensvignetting)andsensornonuniformityInstructions-ResultsUniformity(LightFalloff):ImatestMaster-InstructionsforImatestMasterInputdialogbox-Hotanddeadpixels-Colorshading-Uniformityprofiles-Polynomialfit-Histograms-Noisedetail-SpotdetectionUsingDistortionIntroduction-Instructions-Results-Mainfigure-Decentering-Correctedimage-Intersectionfigure-Radiuscorrectionfig-Links-AlgorithmImatestInstructions--MiscellaneousmodulesandutilitiesUsingTestCharts-CreatestestchartsforhighqualityinkjetprintersIntroduction-Bitmappatterns-SVGpatterns-OptionsUsingScreenPatterns-MonitorpatternsforLightFalloff,SFR,Distortion,andmonitorcalibrationIntroduction-LightFalloff-SFR-Distortion-Monitorcalibration-Monitorgamma-Zoneplate-SMPTEcolorbars-Slantededges-Colorchecker-Stepchart-Squares(checkerboard)SVGTestCharts-ScalableVectorGraphicschartsforMTFmeasurementsIntroduction:mxnsquares-Squaresandwedges-Operation-Options-Outputfigure-PrintingView/RenameFiles-usingEXIFdataStarting-1.Selectfolder-2.Selectfiles-3.Renameoptions-4.Preview-5.RenamefilesImatestIT/EXEinstructions-RunningImatestIT(IndustrialTesting)/EXEIntroduction-Installation-Setup-INIfiles-DOScall-CallingfromMatlab-Testing-ErrorhandlingUsingPrintTest-Measureprintqualityfactors:colorresponse,tonalresponse,andDmaxIntroduction-Instructions-ResultsMaskfill-RemovesfeaturesthatinterferewithImatestmeasurementsImatestDocumentation3of451Introduction-InstructionsAppendixCross-referencetables-TablestohelpyounavigateImatestSuppliers-Imagequalityfactors-Imagequalityfactors-Modules-Testcharts-TestimagesVersioncomparisons-Differencesbetweenversions.Whichisrightforyou?GlossaryGlosarioenEspanolTroubleshooting-WhattodowhenImatestdoesn'tworkInstallationproblems-Problemsafterinstall-MissingDLLs-Runtimeproblems-INIfiles-Command(DOS)window-Diagnosticsruns-PathconflictsImatestChangeLog-ImatestreleasehistoryXMLChanges-NewXMLimprovementsinImatest3.5.1CompletePDFdocumentation-Thewholedocs14MBandalmost500pages,updatedoccasionallyLicense-TheImatestEndUserLicenseAgreement(EULA)ImatestDocumentation4of451ImageQualitySharpnessWhatisitandhowisitmeasured?ImagesharpnessSharpnessisarguablythemostimportantphotographicimagequalityfactor:it'sthefactormostcloselyrelatedtotheamountofdetailanimagecanrender.Butit'snottheonlyimportantfactor.Imatestmeasuresagreatmanyothers.Sharpnessisdefinedbytheboundariesbetweenzonesofdifferenttonesorcolors.Itisillustratedbythebarpatternofincreasingspatialfrequency,below.Thetopportionrepresentsatargetusedtotestacamera/lenscombination.Itissharp;itsboundariesareabrupt,notgradual.Thebottomportionillustratestheeffectofahighquality35mmlensona0.5millimeterlongimageofthepattern(onthefilmordigitalsensorplane).Itisblurred.Alllenses,eventhefinest,blurimagestosomedegree.Poorlensesblurimagesmorethanfineones.Onewaytomeasuresharpnessistousetherisedistanceoftheedge,forexample,thedistance(inpixels,millimeters,orfractionofimageheight)forthepixelleveltogofrom10%to90%ofitsfinalvalue.Thisiscalledthe10-90%risedistance.Althoughrisedistanceisagoodindicatorofimagesharpness,ithasonelimitation.Itispoorlysuitedforcalculatingthesharpnessofacompleteimagingsystemfromthesharpnessofitscomponents,forexample,fromalens,digitalsensor,andsoftwaresharpeningalgorithm.Togetaroundthisproblem,measurementsaremadeinfrequencydomain,wherefrequencyismeasuredincyclesorlinepairsperdistance(typicallymillimetersinfilmmeasurements,butmayalsobeinches,pixels,orimageheight).Linepairspermillimeter(lp/mm)isthemostcommonspatialfrequencyunitforfilm,butcycles/pixelisconvenientfordigitalsensors.Theimagebelowisasinewave—apatternofpuretones—thatvariesfromlowtohighspatialfrequencies,inthiscasefrom2to200lp/mm,overadistanceof0.5millimeters.Thetopportionistheoriginalsinepattern.Thebottomportionillustratestheeffectsofthesamehighquality35mmlens,whichreducespatterncontrastathighspatialfrequencies.Therelativecontrastatagivenspatialfrequency(outputcontrast/inputcontrast)iscalledtheModulationTransferFunction(MTF)orSpatialFrequencyResponse(SFR).IllustrationofModulationTransferFunction(MTF)(Spatialfrequencyresponse(SFR))ImatestDocumentation5of451Greenisforgeeks.Doyougetexcitedbyagoodequation?Wereyoupassionateaboutyourcollegemathclasses?Thenyou'reprobablyamathgeek—amemberofamisunderstoodbuthighlyelitefellowship.Thetextingreenisforyou.Ifyou'renormalormathematicallychallenged,youmayskipthesesections.You'llneverknowwhatyoumissed.Theupperplotdisplaysthesineandbarpatterns:originalandafterblurringbythelens.Themiddleplotdisplaystheluminanceofthebarpatternafterblurringbythelens(theredcurve).Contrastdecreasesathighspatialfrequencies.ThelowerplotdisplaysthecorrespondingMTF(SFR)curve(thebluecurve).Bydefinition,thelowfrequencyMTFlimitisalways1(100%).Forthislens,MTFis50%at61lp/mmand10%at183lp/mm.BothfrequencyandMTFaredisplayedonlogarithmicscaleswithexponentialnotation(100=1;101=10;102=100,etc.).Amplitudeisdisplayedonalinearscale.ThebeautyofusingMTF(SpatialFrequencyResponse)isthattheMTFofacompleteimagingsystemistheproductofthetheMTFofitsindividualcomponents.MTFisrelatedtoedgeresponsebyamathematicaloperationknownastheFouriertransform.MTFistheFouriertransformoftheimpulseresponse—theresponsetoanarrowline,whichisthederivative(d/dx)oftheedgeresponse.Fortunately,youdon'tneedtounderstandFouriertransformsorcalculustounderstandMTF.Traditional"resolution"measurementsinvolveobservinganimageofabarpattern(usuallytheUSAF1951chart)onfilm,andlookingforthehighestspatialfrequency(inlp/mm)whereapatternisvisible.ThiscorrespondstoanMTFofabout5-10%.Becausethisisthespatialfrequencywhereimageinformationdisappears—whereitisn'tvisible,itisnotagoodindicatorofimagesharpness.ExperiencehasshownthatthebestindicatorsofimagesharpnessarethespatialfrequencieswhereMTFis50%ofitslowfrequencyvalue(MTF50)or50%ofitspeakvalue(MTF50P).MTF50orMTF50Pareidealparametersforcomparingthesharpnessofdifferentcamerasforseveralreasons:(1)Imagecontrastishalfitslowfrequencyorpeakvalues,hencedetailisstillquitevisible.(2)TheeyeisrelativelyinsensitivetodetailatspatialfrequencieswhereMTFislow:10%orless.(3)TheresponseofvirtuallyallcamerasfallsoffrapidlyinthevicinityofMTF50andMTF50P.MTF50PmaybetterforoversharpenedcamerasthathavepeaksintheirMTFresponse.AlthoughMTFcanbeestimateddirectlyfromimagesofsinepatterns(seeReschartsLogFrequency,LogF-Contrast,andStarChart),asophisticatedtechnique,basedontheISO12233standard,"Photography-Electronicstillpicturecameras-Resolutionmeasurements,"providesmoreaccurateandrepeatableresults.Aslanted-edgeimage,describedbelow,isphotographed,thenanalyzedbyImatestSFRorReschartsSlanted-edgeSFR.(SFRstandsforSpatialFrequencyResponse.)OriginsofImatestSFRThealgorithmsforcalculatingMTF/SFRwereadaptedfromaMatlabprogram,sfrmat,writtenbyPeterBurns()toimplementtheISO12233standard.ImatestSFRincorporatesnumerousimprovements,includingimprovededgedetection,betterhandlingoflensdistortion,anicerinterface,andfarmoredetailedoutput.TheoriginalMatlabcodeisavailableontheI3AISOtoolsdownloadpagebyclickingonISO12233SlantEdgeAnalysisToolsfrmat2.0.Incomparingsfrmat2.0resultswithImatest,notethatifnoOECF(tonalresponsecurve)fileisenteredintosfrmat,itassumesthatthereisnotonalresponsecurve,i.e.,gamma=1.InImatest,gammaissettoadefaultvalueof0.5,whichistypicalofdigitalcameras.Toobtaingoodagreementwithsfrmat,youmustsetgammato1.Theslanted-edgetestforSpatialFrequencyResponseSlanted-edgetestchartscanbecreatedwithImatestTestCharts(SVGchartsareespeciallyrecommended)ordownloadedfromHowtotestlenseswithImatest.Thebitmapcharthashorizontalandverticaledgesforbestprintquality.ItshouldbeImatestDocumentation6of451tilted(about2-8degrees)beforeitisphotographed.ImatestSFRcanalsotakeadvantageofportionsoftheISO12233testchart,shownontheright,oraderivativeliketheAppliedImageQA-77,orasalessexpensivealternativefromDanes-PictaintheCzechRepublic(theDCR3chartontheirDigitalImagingpage)).Twosuchportionsareindicatedbytheredandbluearrows.ISO12233chartsareusedinimaging-resource.comanddpreview.comdigitalcamerareviews.Aprintablevector-graphicsversionoftheISOchartisavailablecourtesyofStephenH.WestinoftheCornellUniversityComputerGraphicsDepartment.Itshouldbeprintedaslargeaspossible(24incheshighifpossible)soedgesharpnessisnotlimitedbytheprinteritself.(Theremaybesomejaggednessintheslantededges;notaproblemwiththerecommendedprintabletarget.)Atypicalportionisshownontheright:acropofaverticaledge(slantedabout5.6degrees),usedtocalculatehorizontalMTFresponse.Anadvantageoftheslantededgetestisthatthecamera-to-targetdistanceisn'tcritical.Itdoesn'tenterintotheequationthatconvertstheimageintoMTFresponse.ImatestMastercancalculateMTFforedgesofvirtuallyanyangle,thoughexactvertical,horizontal,and45°canhavenumericalproblems.Slantededgealgorithm(calculationdetails)TheMTFcalculationisderivedfromISOstandard12233.SomedetailsarecontainedinPeterBurns'SFRMAT2.0User's