50mm1.4的评测

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1、DistortionsTheEF50mmf/1.4producesaslighttomoderateamountofbarreldistortion(1.1%).Thisisbarelynoticeableinfieldconditions.VignettingUltralargeaperturelenseshaveahardtimeregardingvignettingwhenusedonfullformatDSLRs.TheEF50mmf/1.4USMshowsanextremelyhighamountoflightfalloffatf/

2、1.4-a2.7EVthisisdisturbinginmostimagesunlessyouprefertheeffectforartisticreasons.Theissueimprovessubstantiallywhenstoppingdowntof/2butyouneedtogoforf/2.8orbeyondtoreducethelightfallofftoadegreewhereitisn'tdisturbinganymore.MTF(resolution)Theresolutionchartshowsaratherwidesp

3、readinimagequalityacrossthetestedaperturerangebutthisistypicalformostultra-largeaperturelenses.Thecenterperformanceisverygoodatf/1.4butthebordersarejustonagoodlevelandthecornersaresoft.Thecontrastlevelisalsosomewhatreducedespeciallytowardsthecorners.Thesituationimprovesquit

4、eabitwhenstoppingdowntof/2-thecenterisliftedintoexcellentlevelhereandthecornersstarttogetacceptable.There'safurtherboostoftheborder/cornerqualityatf/2.8-theouterregionreachesverygoodfigureshere(albeitjust).Therangebetweenf/4andf/8representsthesweetspotofthelenswithanoutstan

5、dingcenterresolutionandgenerallyexcellentbordersandcorners.Diffractioneffectsreducetheglobalqualityfromf/11onwardsbutthisis,ofcourse,aphysicallimitationandnotadesignissueofthelens.Belowisasimplifiedsummaryoftheformalfindings.Thechartshowslinewidthsperpictureheight(LW/PH)whi

6、chcanbetakenasameasureforsharpness.IfyouwanttoknowmoreaboutityoumaycheckoutthecorrespondingImatestExplanations.ChromaticAberrations(CAs)Similartomostotherfix-focallenseschromaticaberrations(colorshadowsatharshcontrasttransitions)areverylowandnothingtoworryabout.BokehTheboke

7、h(thequalityoftheout-of-focusblur)isaprimaryaspectforanultralargeaperturelens.Theout-of-focushighlightssuffersomewhatfromvignettingeffectsatf/1.4sotheshapedoesdeterioratesomewhattoa"cat'seye"towardsthecorners.There'salsoanoutliningeffectherebuttheinnerhighlightzoneisverysmo

8、othanduniform.Theoutliningisslightlyimprovedatf/2andit'sgonebyf/2.8.However,starti