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Chapter 2. Inside a Digital Camera

Chapter 2. Inside a Digital Camera

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camerasometimescostasmuchastherestofthecamera)andsalesofsuchan

expensivedevicewerelow.Insteadofdesigninganewcamerabody,vendors

patterneddigitalmodelsonexistingfilmcamerasystemsandusedmanyofthe

sameparts,includinglenses.Thatwascost-effectivefromadevelopmentalpoint

ofview.But,aswe'llsee,thatwasn'taverygoodwayofdesigningadigital

camerawhichhas,afterall,itsownsetofrequirements,rangingfromsensorsize

tolensparameters.

Fortunately,whenthecostofhigh-resolutionsensorsbecamereasonable,new

camerasweredesignedfromscratchtotakeadvantageoftheircapabilities,and

tosellatlowerprices.Today,evenexpensivedigitalcamerasandtheir

accessorieshavelessandlessincommonwiththeirfilmcounterparts.Olympus,

inparticular,withitsFour-Thirdsdesigns,haspioneeredcreatingdigitalcameras

thatarebuiltfromthegrounduptomeettheneedsofelectronicimaging.

Thischapterwillhelpyouunderstandhowdigitalcameraswork.You'llalso

learnaboutthedifferencesbetweenfilmanddigitalcameras,particularlythe

featuresthatdigitalcamerashaveandfilmcamerasdonot.You'llfindthisnutsand-boltsinformationespeciallyusefulwhenshoppingforanewcamera,

becausenoteverycamerahaseveryfeature.Butevenifyoualreadyownthe

digitalcameraofyourdreams,you'llstillfindthischapterhelpfulinsortingout

themostusefulfeaturesfromthosethatarelikelytobemoretroublethanthey

areworth.



GuidedTourofaDigitalCamera

We'regoingtostartwithagenerictourofatypicalnon-SLRdigitalcamera.

Lateron,we'llgetintothefeaturesofdigitalSLRcameras,too,butifyouwanta

greatdealofdetailonhowdSLRswork,Irecommendmycompanionvolume,

MasteringDigitalSLRPhotography.There'smorethanyoueverexpectedto

knowaboutthedigitalsinglelensreflexcamera.

Digitalcamerascomeinmanyshapesandsizes.Yoursmightresembleoneof

thecamerasshowninFigure2.1,whichrangefromultracompactsaboutthesize

ofadeckofcards(likethecamerainfront)tomoresophisticatedmodelslike

thoseshowninthebackrow.

Figure2.1.Digitalcamerascomeinallshapesandsizes.



Digitalmodelslookevenmoredifferentfromtherear.Allofthemwillsportan

LCDviewfinder,butthatLCDmayrangeinsizefromapuny1.5inches

diagonallytothegenerous2.5inchesshowninthemodelinFigure2.2.

Figure2.2.Fromtherear,digitalcamerasareusuallydominatedby

theirLCDsandarrayofcontrols.



Forthischapter,I'vechosentoillustratehowdigitalcamerasworkusinga

medium-rangemodelthathaslotsoffeatures.It'sanelectronicviewfinder(EVF)

model,whichprovidesSLR-likeoperation.ExceptfortheEVF,you'llfindmost

ofthefeaturesinthiscamerainthemajorityofsub-$1,000digitalshooters.

Yourcameramaynotlookexactlylikemyexample,whichisbasedonan

existingcamerabutgenericizedabitinshapeandlayouttomoreclosely

representcamerasthatareonthemarket.Digitalcamerasvarywidelyin

appearance,butallofthemsharecertaincommoncomponents.Althoughthe

locationforindividualcontrolsandfeaturesmaydifferslightly,andthecamera

bodymaybesquare,cubical,orrounded,virtuallyalldigitalcamerashavea

takinglens,anopticalorelectronicviewfinder,acolorLCDdisplaypanelfor

previewinganimageandshowingmenus,ashutterrelease,andaclutchof

controlbuttons.You'llfindthelayoutsinmanycasesaresurprisinglysimilarto

myexample.

Mostalsohaveoneormoreslotsforremovablestorage,suchasSecureDigital

orCompactFlashcards;abuilt-inelectronicflashunit;atop-mounted

monochromeLCDpanel(foundondigitalSLRsfordisplayingthenumberof

remainingexposures,currentcameramode,andotherstatusinformation);anda

serialorUSBportforconnectingthecameratoyourcomputerwhenyouwantto

downloadphotos.Youalsomightfindatripodsocket,oraninfraredportfor

wirelesstransmissionofpictures.



We'lllookatourexamplecamerafromfourdifferentviews:thefront,back,top

plate,andthe"control"side(whichcontainsmanyoftheimportantcontrols).

Theothertwosurfacesoftheaveragedigitalcameraarelessinteresting:the

bottomsidemightcontainatripodsocketandmaybeacompartmentfor

batteries,whiletherightsideisgrippedbythephotographerandusuallyhas

littlemorethanacoverthathidesthedigitalmemorycardaccessslot.

It'spossiblethatnotallthetermsinthefollowingtourwillbefamiliartoyou.I'll

explainaboutshutterspeeds,f-stops,autofocusing,programmedexposures,

singlelensreflexes,andothertopicslaterinthischapter.Considerthisabasic

orientationtour,andfeelfreetocomebackandreviewonceyouarecomfortable

withallthecomponentsofadigitalcamera.

Firstupisthefrontview,showninFigure2.3.I'venumberedthekeyfeatures

andlistedtheirfunctionsbelow.

1. Controlwheel/jogwheel.Thiscontrolisusuallyplacedneartheshutter

releaseoronthebackofthecamerasoitcanbeoperatedeasilybythe

indexfingerorthumboftherighthand.Somecameras,particularlydigital

SLRs,havetwocontrolwheels.Thisdialisusedtochangesettingswhen

thecameraisuptoyoureyejustbeforethephotoistaken.Forexample,

onecameraputsthecontrolwheeltoworkchangingbothshutterspeedand

aperturesettings(dependingonwhethertheshutterspeedorlensopening

controlbuttonsarepressedwiththeotherhand).Thesamecellyourcamerato

add+1EV,itwillprovidetwiceasmuchexposure,eitherbyusingalarger

f-stop,slowershutterspeed,orboth.



eyedropper

Animage-editingtoolusedtosamplecolorfromonepartofanimagesoit

canbeusedtopaint,draw,orfillelsewhereintheimage.Withinsome

features,theeyedroppercanbeusedtodefinetheactualblackpointsand

whitepointsinanimage.



feather

Tofadeoutthebordersofanimageelement,soitwillblendinmore

smoothlywithanotherlayer.



filllighting

Inphotography,lightingusedtoilluminateshadows.Reflectorsor

additionalincandescentlightingorelectronicflashcanbeusedtobrighten

shadows.Onecommontechniqueoutdoorsistousethecamera'sflashasa

fill.



filter

Inphotography,adevicethatfitsoverthelens,changingthelightinsome

way.Inimageediting,afeaturethatchangesthepixelsinanimageto

produceblurring,sharpening,andotherspecialeffects.PhotoshopCS

includesseveralnewfiltereffects,includingLensBlurandPhotoFilters.



FireWire(IEEE-1394)

Afastserialinterfaceusedbyscanners,digitalcameras,printers,andother

devicestotransferinformation.



flashsync

Thetimingmechanismthatensuresthataninternalorexternalelectronic

flashfiresatthecorrecttimeduringtheexposurecycle.AnSLR'sflash

syncspeedisthehighestshutterspeedthatcanbeusedwithflash.Seealso

frontcurtainsyncandrearcurtainsync.



flat

Animagewithlowcontrast.



flatbedscanner

Atypeofscannerthatreadsonelineofanimageatatime,recordingitasa

seriesofsamples,orpixels.



focalplane

Animaginaryline,perpendiculartotheopticalaccess,whichpasses

throughthefocalpointformingaplaneofsharpfocuswhenthelensisset



atinfinity.



focallength

Thedistancebetweenthefilmandtheopticalcenterofthelenswhenthe

lensisfocusedoninfinity,usuallymeasuredinmillimeters.



focus

Toadjustthelenstoproduceasharpimage.



focuslock

Acamerafeaturethatletsyoufreezetheautomaticfocusofthelensata

certainpoint,whenthesubjectyouwanttocaptureisinsharpfocus.



focusrange

Theminimumandmaximumdistanceswithinwhichacameraisableto

produceasharpimage,suchas2inchestoinfinity.

FigureA.8.Fillflashhasbrightenedtheshadowsonthis

mascot'sjersey.



focusservo

Amechanismthatadjuststhefocusdistanceautomatically.Thefocusservo

canbesettosingleautofocus,whichfocusesthelensonlywhentheshutter

releaseispartiallydepressed,andcontinuousautofocus,whichadjusts

focusconstantlyasthecameraisused.



focustracking

Theabilityoftheautomaticfocusfeatureofacameratochangefocusas

thedistancebetweenthesubjectandthecamerachanges.Onetypeoffocus

trackingispredictive,inwhichthemechanismanticipatesthemotionofthe

objectbeingfocusedon,andadjuststhefocustosuit.



four-colorprinting



Anothertermforprocesscolor,inwhichcyan,magenta,yellow,andblack

inksareusedtoreproduceallthecolorsintheoriginalimage.



framing

Inphotography,composingyourimageintheviewfinder.Incomposition,

usingelementsofanimagetoformasortofpictureframearoundan

importantsubject.



frequency

Thenumberoflinesperinchinahalftonescreen.



fringing

Achromaticaberrationthatproducesfringesofcoloraroundtheedgesof

subjects,causedbyalens'inabilitytofocusthevariouswavelengthsof

lightontothesamespot.Purplefringingisespeciallytroublesomewith

backlitimages.



front-curtainsync

Thedefaultkindofelectronicflashsynchronizationtechnique,originally

associatedwithfocalplaneshutters,whichconsistofatravelingsetof

curtains,includingafrontcurtain(whichopenstorevealthefilmorsensor)

andarearcurtain(whichfollowsatadistancedeterminedbyshutterspeed

toconcealthefilmorsensorattheconclusionoftheexposure).



Foraflashpicturetobetaken,theentiresensormustbeexposedatone

timetothebriefflashexposure,sotheimageisexposedafterthefront

curtainhasreachedtheothersideofthefocalplane,butbeforetherear

curtainbeginstomove.

Front-curtainsynccausestheflashtofireatthebeginningofthisperiod

whentheshutteriscompletelyopen,intheinstantthatthefirstcurtainof

thefocalplaneshutterfinishesitsmovementacrossthefilmorsensor

plane.Withslowshutterspeeds,thisfeaturecancreateablureffectfrom

theambientlight,showingaspatternsthatfollowamovingsubjectwith

subjectshownsharplyfrozenatthebeginningoftheblurtrail(thinkofan

imageofTheFlashrunningbackwards).Seealsorear-curtainsync.



frontlighting

Illuminationthatcomesfromthedirectionofthecamera.Seealso

backlightingandsidelighting.

FigureA.9.Extrememagnificationrevealsfringingaroundthe

player'sshoulders,achromaticaberrationcausedbythelens'

inabilitytofocusallthecolorsoflightonthesamespot.



f-stop

Therelativesizeofthelensaperture,whichhelpsdeterminebothexposure

anddepth-of-field.Thelargerthef-stopnumber,thesmallerthef-stop

itself.Ithelpstothinkoff-stopsasdenominatorsoffractions,sothatf2is

largerthanf4,whichislargerthanf8,justas1/2,1/4,and1/8represent

eversmallerfractions.Inphotography,agivenf-stopnumberismultiplied

by1.4toarriveatthenextnumberthatadmitsexactlyhalfasmuchlight.

So,f1.4istwiceaslargeasf2.0(1.4x1.4),whichistwiceaslargeasf2.8

(2x1.4),whichistwiceaslargeasf4(2.8x1.4).Thef-stopswhichfollow

aref5.6,f8,f11,f16,f22,f32,andsoon.



full-colorimage

Animagethatuses24-bitcolor,16.8millionpossiblehues.Imagesare

sometimescapturedinascannerwithmorecolors,butthecolorsare

reducedtothebest16.8millionshadesformanipulationinimageediting.



gamma

Anumericalwayofrepresentingthecontrastofanimage.Devicessuchas

monitorstypicallydon'treproducethetonesinanimageinstraight-line

fashion(allcolorsrepresentedinexactlythesamewayastheyappearinthe

original).Instead,sometonesmaybefavoredoverothers,andgamma

providesamethodoftonalcorrectionthattakesthehumaneye'sperception

ofneighboringvaluesintoaccount.Gammavaluesrangefrom1.0toabout

2.5.TheMacintoshhastraditionallyusedagammaof1.8,whichis

relativelyflatcomparedtotelevision.WindowsPCsusea2.2gammavalue,

whichhasmorecontrastandismoresaturated.



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Chapter 2. Inside a Digital Camera

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