Camera.docx
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Camera.docx
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Camera
Camera
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Forotheruses,seeCamera(disambiguation).
Sectionthroughamodernsingle-lensreflexcamera
Lefttoright:
anAgfaboxcamera,aPolaroidLandcamera,andaYashica35mmSLR
Acameraisadevicethatrecordsimages,eitherasastillphotographorasmovingimagesknownasvideosormovies.Thetermcomesfromthecameraobscura(Latinfor"darkchamber"),anearlymechanismofprojectingimageswhereanentireroomfunctionedasareal-timeimagingsystem;themoderncameraevolvedfromthecameraobscura.
Camerasmayworkwiththelightofthevisiblespectrumorwithotherportionsoftheelectromagneticspectrum.Acameragenerallyconsistsofanenclosedhollowwithanopening(aperture)atoneendforlighttoenter,andarecordingorviewingsurfaceforcapturingthelightattheotherend.Amajorityofcamerashavealenspositionedinfrontofthecamera'sopeningtogathertheincominglightandfocusallorpartoftheimageontherecordingsurface.Thediameteroftheapertureisoftencontrolledbyadiaphragmmechanism,butsomecamerashaveafixed-sizeaperture.
Atypicalstillcameratakesonephotoeachtimetheuserpressestheshutterbutton.Atypicalmoviecameracontinuouslytakes24filmframespersecondaslongastheuserholdsdowntheshutterbutton.
Contents
[hide]
∙1History
∙2Mechanics
o2.1Imagecapture
o2.2Lens
o2.3Focus
o2.4Exposurecontrol
o2.5Shutters
∙3Filmformats
∙4Cameradesigns
o4.1Platecamera
o4.2Largeformatcamera
o4.3Foldingcamera
o4.4Boxcamera
o4.5Rangefindercamera
o4.6Single-lensreflex
o4.7Twin-lensreflex
o4.8Cinécamera
∙5Imagegallery
∙6Seealso
o6.1Types
o6.2Brands
o6.3Other
∙7References
∙8Externallinks
[edit]History
Mainarticle:
Historyofthecamera
Cameraobscura.
Theforerunnertothecamerawasthecameraobscura.[1]Thecameraobscuraisaninstrumentconsistingofadarkenedchamberorbox,intowhichlightisadmittedthroughaconvexlens,forminganimageofexternalobjectsonasurfaceofpaperorglass,etc.,placedatthefocusofthelens.[2]ThecameraobscurawasfirstinventedbytheIraqiscientistIbnal-Haytham(Alhazen)asdescribedinhisBookofOptics(1015-1021).[3]IrishscientistRobertBoyleandhisassistantRobertHookelaterdevelopedaportablecameraobscurainthe1660s.[4]
ThefirstcamerathatwassmallandportableenoughtobepracticalforphotographywasbuiltbyJohannZahnin1685,thoughitwouldbealmost150yearsbeforetechnologycaughtuptothepointwherethiswaspractical.EarlyphotographiccameraswereessentiallysimilartoZahn'smodel,thoughusuallywiththeadditionofslidingboxesforfocusing.Beforeeachexposure,asensitizedplatewouldbeinsertedinfrontoftheviewingscreentorecordtheimage.JacquesDaguerre'spopulardaguerreotypeprocessutilizedcopperplates,whilethecalotypeprocessinventedbyWilliamFoxTalbotrecordedimagesonpaper.
Thefirstpermanentcolourphotograph,takenbyJamesClerkMaxwellin1861.
Thefirstpermanentphotographwasmadein1826byJosephNicéphoreNiépceusingaslidingwoodenboxcameramadebyCharlesandVincentChevalierinParis.NiépcebuiltonadiscoverybyJohannHeinrichSchultz(1724):
asilverandchalkmixturedarkensunderexposuretolight.However,whilethiswasthebirthofphotography,thecameraitselfcanbetracedbackmuchfurther.Beforetheinventionofphotography,therewasnowaytopreservetheimagesproducedbythesecamerasapartfrommanuallytracingthem.
ThedevelopmentofthecollodionwetplateprocessbyFrederickScottArcherin1850cutexposuretimesdramatically,butrequiredphotographerstoprepareanddeveloptheirglassplatesonthespot,usuallyinamobiledarkroom.Despitetheircomplexity,thewet-plateambrotypeandtintypeprocesseswereinwidespreaduseinthelatterhalfofthe19thcentury.Wetplatecameraswerelittledifferentfrompreviousdesigns,thoughthereweresomemodels,suchasthesophisticatedDubroniof1864,wherethesensitizinganddevelopingoftheplatescouldbecarriedoutinsidethecameraitselfratherthaninaseparatedarkroom.Othercameraswerefittedwithmultiplelensesformakingcartesdevisite.Itwasduringthewetplateerathattheuseofbellowsforfocusingbecamewidespread.
ThefirstcolourphotographwasmadebyScottishphysicistJamesClerkMaxwell,withthehelpofEnglishinventorandphotographerThomasSutton,in1861[5]
[edit]Mechanics
[edit]Imagecapture
seealsoPhotographiclensdesign
19thcenturystudiocamera,withbellowsforfocusing.
Traditionalcamerascapturelightontophotographicfilmorphotographicplate.Videoanddigitalcamerasuseelectronics,usuallyachargecoupleddevice(CCD)orsometimesaCMOSsensortocaptureimageswhichcanbetransferredorstoredintapeorcomputermemoryinsidethecameraforlaterplaybackorprocessing.
CamerasthatcapturemanyimagesinsequenceareknownasmoviecamerasorascinécamerasinEurope;thosedesignedforsingleimagesarestillcameras.Howeverthesecategoriesoverlap.Asstillcamerasareoftenusedtocapturemovingimagesinspecialeffectsworkandmoderndigitalcamerasareoftenabletotriviallyswitchbetweenstillandmotionrecordingmodes.Avideocameraisacategoryofmoviecamerathatcapturesimageselectronically(eitherusinganalogueordigitaltechnology).
[edit]Lens
Mainarticle:
Photographiclens
Mainarticle:
Photographiclensdesign
Thelensofacameracapturesthelightfromthesubjectandbringsittoafocusonthefilmordetector.Thedesignandmanufactureofthelensiscriticaltothequalityofthephotographbeingtaken.Thetechnologicalrevolutionincameradesigninthe18thcenturyrevolutionisedopticalglassmanufactureandlensdesignwithgreatbenefitsformodernlensmanufactureinawiderangeofopticalinstrumentsfromreadingglassestomicroscopes.PioneersincludedZeissandLeitz.
[edit]Focus
Auto-focussystemscancaptureasubjectavarietyofways;here,thefocusisontheperson'simageinthemirror.
Duetotheopticalpropertiesofphotographiclenses,onlyobjectswithinalimitedrangeofdistancesfromthecamerawillbereproducedclearly.Theprocessofadjustingthisrangeisknownaschangingthecamera'sfocus.Therearevariouswaysoffocusingacameraaccurately.Thesimplestcamerashavefixedfocusanduseasmallapertureandwide-anglelenstoensurethateverythingwithinacertainrangeofdistancefromthelens,usuallyaround3metres(10ft)toinfinity,isinreasonablefocus.Fixedfocuscamerasareusuallyinexpensivetypes,suchassingle-usecameras.Thecameracanalsohavealimitedfocusingrangeorscale-focusthatisindicatedonthecamerabody.Theuserwillguessorcalculatethedistancetothesubjectandadjustthefocusaccordingly.Onsomecamerasthisisindicatedbysymbols(head-and-shoulders;twopeoplestandingupright;onetree;mountains).
Rangefindercamerasallowthedistancetoobjectstobemeasuredbymeansofacoupledparallaxunitontopofthecamera,allowingthefocustobesetwithaccuracy.Single-lensreflexcamerasallowthephotographertodeterminethefocusandcompositionvisuallyusingtheobjectivelensandamovingmirrortoprojecttheimageontoagroundglassorplasticmicro-prismscreen.Twin-lensreflexcamerasuseanobjectivelensandafocusinglensunit(usuallyidenticaltotheobjectivelens.)inaparallelbodyforcompositionandfocusing.Viewcamerasuseagroundglassscreenwhichisremovedandreplacedbyeitheraphotographicplateorareusableholdercontainingsheetfilmbeforeexposure.Moderncamerasoftenofferautofocussystemstofocusthecameraautomaticallybyavarietyofmethodse.g.byfishing.[6]
[edit]Exposurecontrol
Thesizeoftheapertureandthebrightnessofthescenecontrolstheamountoflightthatentersthecameraduringaperiodoftime,andtheshuttercontrolsthelengthoftimethatthelighthitstherecordingsurface.Equivalentexposurescanbemadewithalargerapertureandafastershutterspeedoracorrespondingsmallerapertureandwiththeshutterspeedsloweddown.
[edit]Shutters
Mainarticle:
Shutter(photography)
Althougharangeofdifferentshutterdeviceshavebeenusedduringthedevelopmentofthecameraonlytwotypeshavebeenwidelyusedandremaininusetoday.
Thefocalplaneshutteroperatesasclosetothefilmplaneaspossibleandconsistsofclothcurtainsthatarepulledacrossthefilmplanewithacarefullydeterminedgapbetweenthetwocurtainsorconsistingofaseriesofmetalplatesmovingeitherverticallyorhorizontallyacrossthefilmplan.Asthecurtainsorbladesmoveataconstantspeed,exposingthewholefilmplanecantakesmuchlongerthantheexposuretime.Forexampleanexposureof1/1000secondmaybeachievedbytheshuttercurtainsmovingacrossthefilmplanein1/50thofasecondbutwiththetwocurtainsonlyseparatedby1/20thoftheframewidth.Whenphotographingrapidlymovingobjects,theuseofafocalplaneshuttercanproducesomeunexpectedeffects.Focalplaneshuttersarealsodifficulttosynchronisewithelectronicflashanditisoftenonlypossibletouseflashatshutterspeedsbelow1/60thsecondalthoughinsomemoderncamerasthatcanbeasfastas1/100second/
TheCopalshutterormorepreciselythein-lensshutterisashuttercontainedwithinthelensstructure,oftenclosetothediaphragmconsistingofaanumberofmetalleaveswhicharemaintainedunderspringtensionandwhichareopenedandthenclosedwhentheshutterisreleased.Thee
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