佳能镜头Canon EF 100mm f2.8 USM macro

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1、IntroductionTheCanonEF100mmf/2.8USMmacrowasintroducedbackinmarch2000replacingtheoldEF100mmf/2.8macro(featuringaclassicmicromotor).OnAPS-CDSLRsthefield-of-viewresemblesa160mmfullformatequivalent.Theprimaryapplicationofthelensis,obviously,macrophotographybutit'snotlimitedtothat-infinityfoc

2、usispossible.Note:theimageaboveshowsthelenswithan(optional)filterattachedandthe(alsooptional)lenshoodhasbeencutdowninlength.ThelenshasbeencompletelyredesignedintoatrueIF(internalfocus)constructionthatdoesnotextendwhenfocusingtomacrodistances.Thisishighlyunusualfora100mmmacrolens.Thefront

3、elementdoesnotrotatesousingapolarizerisnotproblem.Typicalforring-typeUSMlensesfull-timemanualoverrideisalwayspossibleinone-shotAFmode.TheAFspeedisblazinglyfast(anotheruniquepoint)butCanonstillprovidedafocuslimiterinordertoavoidanyAFhuntingintotheextrememacrorangewhenoperatingthelensatnor

4、malfocusdistances.Theminimalfocusdistanceis0.31m(149mmworkingdistance)resultinginamax.magnificationof1:1.Thebroad,rubberizedfocusringandhassmooth,pleasantoperation.Thebuildqualityisverydecentwithametalmountandanouterbarrelmadeofgoodqualityplastics.Theopticalconstructionismadeof12elements

5、in8groupswithoutanyspecialelements.Thelensfeatures8apertureblades.Typicalforalltruemacrolensesitfeaturesafloatingsysteminordertoachieveaconstantperformancethroughoutallfocusingdistances.Thefiltersizeis58mm.Withaweightof600gandasizeof79x119mmitisfairlycompactandaboutcomparabletotherestoft

6、heganginthisclass.Italsoapossibletouseanoptionaltripodmountwhichcanbeattachedtotherearofthelens.Whilenotreallyrequiredthetripodmountprovidesabetterbalance-otherwisethecameralenscombinationtendstobesomewhatfrontloadedspecificallywhenusedonlight-weightDSLRs.DistortionsAsexpectedforafix-foc

7、allensandespeciallyforamacrolensthelevelofdistortionsisabsolutelynegligible.Thechartabovehasareal-worldsizeofabout120x80cm.VignettingOntheEOS350Dwithitsreducedformat(APS-C)the(fullformat)lensexhibitsmoderatevignettingatf/2.8whichdisappearsfromf/4&up.Expectmorevignettingon