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《佳能鏡頭Canon EF 100mm f2.8 USM macro》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在教育資源-天天文庫。
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
