諾基亞-808PureView-相機說明書

PureViewimagingtechnology.

ThispaperdescribesNokia’snewPureViewProimagingtechnology

aswellastheproduct,Nokia808PureView,featuringit.

TheNokiaPureViewProimagingtechnologyisthecombinationofalarge,superhighresolution

41MpixwithhighperformanceCarlZeissoptics.Thelargesensorenablespixeloversampling,which

willbeexplainedindetailinthispaperbutinanutshellitmeansthecombinationofmanypixelsinto

oneperfectpixel.PureViewimagingtechnologyistheresultofmanyyearsofresearchand

developmentandthetangiblefruitsofthisworkareamazingimagequality,losslesszoom,

andsuperiorlowlightperformance.

Arevolutioninimaging

PureViewProimagingtechnologydoesn’t

representastepchangeforcamera

smartphonesperformance,somuchasa

quantumleapforward.Thefirstdevicetofeature

NokiaPureViewProcameratechnologyisthe

Nokia808PureView,whichgivespeoplethe

meanstotakebetterimagesandvideofootage

thaneverbefore.

NokiaPureViewProturnsconventionalthinking

onitshead.Itdispenseswiththeusualscaling/

interpolationmodelofdigitalzoomusedin

virtuallyallsmartphones,aswellasopticalzoom

usedinmostdigitalcameras,whereaseriesof

lenselementsmovesbackandforthtovarythe

magnificationandfieldofview.Instead,we’ve

takenacompletelynewroad.

Theresult?

Unprecedentedcameracontrolandversatility,combinedwithtrulyspectacular-qualityimagesand

video.Nokia808PureViewsetsnewindustrystandards—itwillgiveyouaround3xlosslesszoomfor

stills,and4xzoominfullHD1080p.For720pHDvideo,you’relookingat6xlosslesszoom.

AndfornHD(640x360)video,anamazing12xzoom!

?2012Nokia

2

PureViewimagingtechnology.

Sohowisthispossible?

Thestartingpointisasuper-high-resolutionsensor.Thishasanactiveareaof7728x5368pixels,

totallingover41Mpix.Dependingontheaspectratioyouchoose,itwilluse7728x4354pixelsfor

16:9images/videos,or7152x5368pixelsfor4:3images/videosasisshowninFigure1.

Figure1.Theimagecircleandthe16:9and4:3imageareas

Whathappensnextdependsonthesettingsandwhetherornotyou’reusingzoom.Buttogiveyou

anidea,thedefaultstillimagesettingis5Mpixat16:9,andforvideoit’s1080pat30fps.Usingthese

settings,thezoomisaround3xforstillsand4xforvideo.Conventionalzoomtendstoscaleupimages

fromarelativelylowresolution,resultinginpoorimagequality.Wewereconvincedtheremustbea

betterway,andwefoundit.

Alwaystruetotheimage

WiththeNokiaN8,welimitedthedigitalzoomtojust2xtoavoidtoomuchcompromisetoimage

quality.Butattheendoftheday,thiswasstillaconventionaldigitalzoom.WiththeNokia808PureView,

zoomishandledcompletelydifferently—likenothingthathasgonebefore.We’vetakentheradical

decisionnottouseanyupscalingwhatsoever.Thereisn’tevenasettingforit.

WhenyouzoomwiththeNokia808PureView,ineffectyouarejustselectingtherelevantareaofthe

sensor.Sowithnozoom,thefullareaofthesensorcorrespondingtotheaspectratioisused.Thelimit

ofthezoom(regardlessoftheresolutionsettingforstillsorvideo)isreachedwhentheselectedoutput

resolutionbecomesthesameastheinputresolution.

?2012Nokia

3

PureViewimagingtechnology.

Forexample,withthedefaultsettingof5Mpix(3072x1728),oncetheareaofthesensorreaches

3072x1728,you’vehitthezoomlimit.Thismeansthezoomisalwaystruetotheimageyouwant.

Newdepth,newdetail

ThewayNokiaPureViewProzoomworksgivesyoumanybenefits.Butthemainoneisundoubtedly

‘pixeloversampling’.

Pixeloversamplingcombinesmanypixelstocreateasingle(super)pixel.Whenthishappens,youkeep

virtuallyallthedetail,butfilterawayvisualnoisefromtheimage.Thespeckled,grainylookyoutendto

getinlow-lightingconditionsisgreatlyreduced.Andingoodlight,visualnoiseisvirtuallynon-existent.

Whichmeanstheimagesyoucantakearemorenaturalandbeautifulthanever.Theyarepurer,perhaps

amoreaccuraterepresentationoftheoriginalsubjectthanhaseverbeenachievedbefore.

Figure2.Oversamplingvs.Zoominthecaseof4:3aspectratio

Thelevelofpixeloversamplingishighestwhenyou’renotusingthezoom.Itgraduallydecreasesuntil

youhitmaximumzoom,wherethereisnooversampling.Atthisstage,NokiaPureViewProoptics

andpixelsstartbehavinginamoreconventionalway.Butbecauseonlythecentreoftheopticsare

usedwherethereislessdiffraction,yougetbetteropticalperformance—includinglowdistortion,no

vignetting,andhighlevelsofresolveddetail.Andbecauseallofthisistakencareofforyou,youdon’t

needtothinkaboutit,thesystemgivesyouthebestbalancebetweenzoomandoversamplingbased

onhowyouframeandcomposethesceneorsubject.

Thereareplentymoreadvantages…

?2012Nokia

4

PureViewimagingtechnology.

Purityofdetail.

EvendigitalSLRimageshaveacertainsoftness.Withoversampling,however,imagescanbenoisefree,

yetincrediblydetailedanddefined.Zoomintothe5Mpiximagesat100%magnificationonyourPC

screen,andyou’llsee.There’ssomethingbeautifullypureaboutthedetail—notenhancedinanyway.

Lookcloselyatsomegrass…it’samazing.

Fastershutterspeeds.

WiththeNokia808PureView,yougeteffectivemaximumaperturethroughoutthezoomrange.

Whereaswithopticalzoom,lesslighttendstoreachthesensorasthezoomincreases.Atmaximum

zoom,5.4xmorelightreachestheNokiaPureViewProsensorthanabroadlyequivalentoptical-zoom

digitalcamera(f/5.6asopposedtof/2.4).Andthismeansyougetthebenefitoffastershutterspeeds.

e.g.IfaconventionaldigitalcamerasettoISO100usesashutterspeedof1/30thsecond,

theNokia808PureViewuses1/180thsecondinthesamelightingconditions.Or,lookingat

itanotherway,ifadigitalcamerausesISO600forashutterspeedof1/30th,theNokia808

PureViewcouldmaintainthesameshutterspeedwithISO100—significantlyreducingthe

visualnoiseyou’dseeintheresultingimage.ThisalsomeansthattheNokia808PureView’s

effectiveflashrangeisvirtuallymaintainedatallzoomlevels,ratherthanbeingsignificantly

reducedasthezoomincreases.

Goodbyetodistortion.

Distortiononallimagesisnegligible.Whereaswithopticalzoom,imagestendtogetmoredistorted

towardstheedgeoftheframe(withbentverticalandhorizontallines)atthetopofthezoomrange.

Silentzoom.

Thezoomfunctioniscompletelysilent—whichisreallyimportantwhenshootingvideo.

Lessismore.

ThesimplestructureofNokiaPureViewProbeatsmorecomplicateddesignshandsdown.Image

definitionispinsharp,waysuperiortoconventionalzoomdesigns.Conventionaldesignsneedmany

morelenselementstoprovidethezoomcapabilityandcorrectaberrations,buttheseinterferewith

definitionand/orlighttransmission.Oursimplestructurehasenabledasignificantimprovementin

manufacturingprecision,andourlensesareproducedwith10xgreaterprecisionthanSLRlenses.

ThiswasessentialtoallowthePureViewProsensorandopticstoworkincompletesynergy.

Neatandcompact.

ThesizeoftheNokia808PureViewcamera(includingsensorandoptics)isatleast50%-70%smaller

thanaconventionalopticalzoomdesign.

?2012Nokia

5

PureViewimagingtechnology.

Effectivezoomsettings.

Youcangetrightupclosewithanyzoomsetting.Typically,opticalzoomgetsclosestwithwide

(ratherthantele)lenssettings.Whichmeansyouhavetostandphysicallyclosertowhateveryou’re

shooting,obscuringthelightandpossiblycastingunwantedshadows.WiththeNokia808PureView,

youcanusefullzoomcapabilityatashootingdistanceof15cmprovidinggreaterthanever

magnificationofsmallobjectswithfullzoom.

Onamoretechnicalnote...

oversamplingeliminatesBayerpatternproblems.Forexample,conventional8MPixsensorsincludeonly

4Mpixgreen,2Mpixredand2Mpixbluepixels,whichareinterpolatedto8MpixR,G,Bimage.Withpixel

oversampling,allpixelsbecometrueR,G,andBpixels.What’smore,basedonNyqvisttheorem,you

actuallyneedoversamplingforgoodperformance.Forexample,audioneedstobesampledat44kHz

togetgood22kHzquality.

Longfocallength.

Mostsmartphoneshavequitesmallsensors,sofocallengthsareshort(lessthan4mm),creatinga

wide-rangingdepthoffield.Forsomesituations—grabshots,landscapes,architectureetc—that’s

great.Butyou’relessabletouseareduceddepthoffieldtofocusattentiononthesubject.TheNokia

808PureViewcombinesalongerfocallength(8.02mm)withlargef/2.4aperture—shootingatcloser

distances,the‘bokeh’effectisstriking.

Quality,notquantity

PeoplewillinevitablyhomeinonthenumberofpixelstheNokia808PureViewpacks,butthey’re

missingthepoint.The‘bigdeal’ishowthey’reused.AtNokia,ourfocushasalwaysbeencapability

andperformance.

Themainwaytobuildsmallercamerasovertheyearshasbeentoreducethepixelsize.Thesehave

shrunkjustoverthepast6yearsfrom2.2microns,to1.75microns,to1.4microns(whichiswhere

mostcompactdigitalcamerasandsmartphonesaretoday).Somenewproductsareonthewaywith

1.1micronpixels.Buthere’stheproblem.Thesmallerthepixel,thelessphotonseachpixelisableto

collect.Lessphotons,lessimagequality.There’salsomorevisualnoiseinimages/videos,andvarious

otherknockoneffects.Inourexperience,whennew,smallerpixelsizesensorsarefirstreleased,they

tendtobeworsethanthepreviousgeneration.Whileothersjumpin,bankingonpixelnumbersinstead

ofperformance,weprefertoskipearlyiterations.

?2012Nokia

6

PureViewimagingtechnology.

Lessonslearned

Withthe12MpixNokiaN8,forexample,weweremoreconcernedwithcapturingphotonsoflightthan

rampingupthenumberofmegapixels.Webuckedthetrendandwentwithalargesensorand1.75

micronpixels—buttheresultwasanewbenchmarkinimageandvideoquality.ThissettheNokiaN8

apartatthetime,andcompetitorsarestilltryingtomatchittwoyearslater.TheNokiaPureViewPro

comesisequippedwithanevenlargersensor,1/1.2”approximately2.5largerthanthesensorused

intheNokiaN8.Theresultisanevenlargerareatocollectphotonsoflight.WithPureViewwe’re

continuingtomakechoicesfocusedonperformanceratherthanpixelsforpixels’sake.Fewerbut

betterpixelscanprovidenotjustbetterimageandvideoquality,butbetteroveralluserexperience

andsystemcapability.

Infact,5Mpix-6MpixismorethanenoughforviewingimagesonPC,TV,onlineorsmartphones.

Afterall,howoftendoweprintimagesbiggerthanevenA4?

Whythemegapixelfixation?

Itallstemsfromtheveryearlydaysofdigitalcameras,whenimagequalitywasaffectedbythelimited

numberofpixelsavailable.Asthepixelnumbersincreased,imagequalitydramaticallyimproved.

However,oncetheresolutionreachedaround5Mpix-6Mpix,thereal-worldbenefitsbecamedebatable.

Butbythen,themarkethadmadeadirectcorrelationbetweennumberofpixelsandqualityofimage.

Themorepixelsthebetter,wasthereceivedwisdom.Andthisthinkinghasstuck.Thoughtoday

manufacturerswouldhappilyreducethenumberofpixelsintheircameras,andinsteadconcentrateon

theirlensesandsensors,they’renotsosurethemarketwouldacceptthis.

Butlet’sconsiderwhyyoumightneedmorethan5Mpix.Themostpopularargumentwehearisthe

versatilitytheextrapixelsprovide.Specificallytheabilitytocropimagesorcreatelargeprints.

Cropping

WiththeNokia808PureView,youcanframeyourshotsonthespot.However,ifyouprefer,youcan

deferframinguntillater,asthereisausersettingintheCreativeShootingModeforcapturing

‘full-resolution’images.Youcanchoosetozoomintoanypartoftheimage,andfindnewcreative

viewsintheoriginal.

Actually,wethoughtpeoplemightwanttodoboth,sowedecidedtomakeitaseasyaspossibleto

switch.Wehopethiswillopenupgreatercreativityincomposition—youcanshootquicklyandcrop

laterwhenyouhavemoretimeandalargerdisplaytoworkwith.Youcanre-frameasmanytimesasyou

like,scaletheimagetoyourpreferredoutputresolution,andchoosetherelevantdownscalingmethod

dependingonwhatyouwanttodowithit.

?2012Nokia

7

PureViewimagingtechnology.

Printing

Ifyourarelyprintyourimagesordon’tneedthemlargerthanA3size,5Mpixismorethanenough.

Infact,youcangetsuperbposterprintsaslargeas50x75cm(thesizelimitofmostcommercial

printers)fromverygoodquality3Mpiximages.Ofcourse,ifyourneedsaredifferent,thereisahigher

resolution8Mpixsettinganda‘fullresolution’modeontheNokia808PureView.

IfyouonlyeverviewimagesonTV,PCortablet,oruploadtosocialsharingsites,we’veprovidedanideal

2Mpixlower-resolutionsetting.Oversamplingisevengreaterhere,andthere’sanincreasedlossless

zoomrangetoo,ascanbeseeninFigure2.

Introducing…SlideZoom

TheNokia808PureViewusesanewzoomconceptcalledSlideZoom.Conventionalzoomcanbeslow

andimprecise,andsometimesyouneedtomakeadjustmentstogettheexactframingyouneed.

PinchtoZoomisgreatforviewingafterwards,butnotsogoodforcomposition,especiallyvideo,

whereyouneedsmoothnessofmovement.

SlideZoomisfast,directandprecise—itgetstheframingrightfirsttime.Allyouhavetodoisslide

yourfingerupordownonthedisplaytointeract.There’snoneedtotouchaspecificUIelementon

thedisplay.

Asyoumoveyourfingeronthedisplay,a‘frame’appearsonthescreenwhichmovesinsyncwithyour

finger.Thisallowsyoutopreviewtheframingbeforecommitting,whichisparticularlyusefulforvideo

recording.Themomentyouliftyourfingerfromthedisplay,itzoomsdirectlytothissetting.

AndbecausezoomingusestheNokiaPureViewProsensorratherthanmovingoptics,it’ssilenttoo.

Moreprocessingpower

OneofthereasonstheNokia808PureViewhastakensolongtodevelopisdowntoprocessingpower.

Wesimplycouldn’tgetholdofenough.Eventhemostpowerfulmobilechipsetshaveanupperlimitof

around20Mpiximageprocessingcapability.TheNokia808PureVieweatsupmorethandoublethat.

Forvideo,theamountofpixelshandledthroughtheprocessingchainisstaggering—over1billion

pixelspersecond,and16xoversampling.That’sathroughputofpixels16timesgreaterthanmany

othersmartphones.

Mostsmartphonemanufacturerscropoffasectionofthesensortoeasetheprocessingload.

Bycontrast,theNokia808PureViewhasnolimitedfieldofview.Plus,itprovideslosslesszooming

capability,whichisoutputresolutiondependent.FullHD1080pgivesyou4xzoom.

?2012Nokia

8

PureViewimagingtechnology.

For720pHDvideo,you’relookingat6xlosslesszoom.AndfornHD(640x360)video,anamazing12x

zoom!Inaddition,weareencodingatupto25mbpsinhighprofileH.264format.

Tomakethisallhappen,wedevelopedasensorwithaspecialcompanionprocessorthathandlespixel

scalingbeforesendingtherequirednumbertothemainimageprocessor.

LiketheNokiaN8beforeit,andafewotherNokiasmartphones,theNokia808PureViewrecordstrue

stereoaudio.Mostsmartphonesrecordonlymono,whilesomeinferstereobyusingdual

monorecording.

Incombinationwiththeworld’sfirstimplementationofNokiaRichRecordingtechnology,Nokia808

PureViewrecordsbestinclassstereoaudiowitheverydetail.Whilstmosthighendsmartphonescan

onlyrecordwithoutdistortiontoaround110db,theNokia808cancomfortablycontinuetoaround

140-145db,whichis4timeslouderthanconventionalmicscanrecord.ApartfromthatNokiaRich

Recordingcanalsorecordverylowfrequenciesalsowithoutanydistortion.Thecombinationofallof

theseelementsmeanstheNokia808recordsaudiowithalmostCDlikequality.Ithastobeheardtobe

believed.Intermsofbothvisualandaudibleperformance,theNokia808simplyhasnoequal.

Improvedvideoautofocus

Videoautofocuswasanareathatneededtobedramaticallyimproved.BecauseofNokia808PureView’s

muchlargerimagesensor(5xlargerthanrivalsmartphones)theopticsgiveyouarelativelyshallow

depthoffield.What’smore,we’realsousingoversamplingtechniquesinvideotoachieveourholygrail

oflowvisualnoisewithextremelyhighlevelsofdetail.

Asaresult,wemadeourautofocussystemmoreprecise,sensitiveandcontrollable.Yougetcontinuous

autofocusinallshootingmodes,butwe’vealsoprovidedeasyaccesstoanOn/Offcontrol.InOffmode,

thelensissettohyperfocal,makingiteasiertogetacceptablefocusacrossawiderangeofsubject

distanceswhileeliminatingfocushunting.There’salsoTouchAutofocusforvideoandstillimages.

InCreativeShootingmode,we’vegoneevenfurther.Alongtouchontheviewfinderwillbringupa

pop-upUIwindow,whereyoucanselectAutomaticorMacro.Close-upfocusismuchimprovedinMacro,

whileAutomaticdoesalltheworkforyou.

?2012Nokia

9

PureViewimagingtechnology.

Thetechnology:

PureViewProimagingspecifications

?41Mpixsensorwithpixeloversampling

?Losslesszoom:3xforstills,4xforfullHD1080pvideo

?CarlZeissoptics

Theproduct:

Nokia808PureViewlensandsensorspecifications

?CarlZeissOptics

?Focallength:8.02mm

?35mmequivalentfocallength:26mm,16:9|28mm,4:3

?F-number:f/2.4

?Focusrange:15cm–Infinity(throughoutthezoomrange)

?Construction:

·5elements,1group.Alllenssurfacesareaspherical

·Onehigh-index,low-dispersionglassmouldlens

·Mechanicalshutterwithneutraldensityfilter

?Opticalformat:1/1.2”

?Totalnumberofpixels:7728x5368

?PixelSize:1.4microns

?2012Nokia

10

PureViewimagingtechnology.

PureViewimagingtechnology

WrittenbyJuhaAlakarhu,DamianDinning,andEeroSalmelin

onbehalfofmanydedicatedNokiaimagingexperts

?2012Nokia?2012Nokia

1

PureViewimagingtechnology.

ThispaperdescribesNokia’snewPureViewProimagingtechnology

aswellastheproduct,Nokia808PureView,featuringit.

TheNokiaPureViewProimagingtechnologyisthecombinationofalarge,superhighresolution

41MpixwithhighperformanceCarlZeissoptics.Thelargesensorenablespixeloversampling,which

willbeexplainedindetailinthispaperbutinanutshellitmeansthecombinationofmanypixelsinto

oneperfectpixel.PureViewimagingtechnologyistheresultofmanyyearsofresearchand

developmentandthetangiblefruitsofthisworkareamazingimagequality,losslesszoom,

andsuperiorlowlightperformance.

Arevolutioninimaging

PureViewProimagingtechnologydoesn’t

representastepchangeforcamera

smartphonesperformance,somuchasa

quantumleapforward.Thefirstdevicetofeature

NokiaPureViewProcameratechnologyisthe

Nokia808PureView,whichgivespeoplethe

meanstotakebetterimagesandvideofootage

thaneverbefore.

NokiaPureViewProturnsconventionalthinking

onitshead.Itdispenseswiththeusualscaling/

interpolationmodelofdigitalzoomusedin

virtuallyallsmartphones,aswellasopticalzoom

usedinmostdigitalcameras,where