Thesensitivityofthefilm
Thesensitivityofthefilmtolightiscalledthesensitivityofthefilm.Whentheunexposedfilmencounterslight,achemicalreactionoccursonthefilm.Dependingonhowmuchlightenters,thefilmwillhavedifferentshadesofchangeatdifferentpositions,therebyleavinganimageonthefilm.
Itisworthmentioningthatalthoughitistroublesometoreplacethefilm,inactualshooting,duetovariousconditions,sometimestheuseofhigh-sensitivityfilmwillbecomeanecessarychoice.Sportsphotographersoftenusehigher-sensitivityfilm,becauseiftheydonotuseit,theywillhavetoslowdowntheshutterspeedtoincreasetheamountoflight,whichwillresultinblurryphotosandlossofusefulness.
Sensitivityofdigitalcamera
Digitalcameradoesnothavenegativefilmandchemicalreactiononnegativefilm.Itssensitivityisanindexsimilartofilmsensitivity.Kindofequivalentsensitivity.Infact,theISOofadigitalcameraisachievedbyadjustingthesensitivityofthephotosensitiveelementtolightormergingthephotosensitivepoints,thatistosay,byimprovingthelightsensitivityofthephotosensitiveelementormergingseveraladjacentpixelstoincreasetheISO.thegoalof.
Conversionbetweentwoscales
Introduction
WhenconvertingfromthelogarithmicDINsensitivityvalueS°totheexpressionASAThesensitivityvalueSiscalculatedbythefollowingequation:
Thecalculatedresultisroundedtothenearestinteger.Rearrangetheaboveequations,andthereverseconversionequationisasfollows:
Theresultofthesamecalculationisroundedtothenearestinteger.Thebaseofloghereis10.
Comparisonofcurrentscales
Thefollowingtableshowsthecomparisonofvarioussensitivityscales:
| Table1.Comparisonofvariousdifferentsensitivityscales | |||
| ISOcalculationscale(ASAscale) | ISOlogarithmicscale(DINscale) | GOST(Early1987intheSovietUnion) | Negativeproductswithcorrespondingsensitivity |
|---|---|---|---|
| 1 | 1° | SvemaMicrat-orto,AstrumMicrat-orto | |
| 3 | 6° | 2.8 | SvemaMZ-3,AstrumMZ-3 |
| 6 | 9° | OriginalKodachrome | |
| 8 | 10° | PolaroidPolaBlue | |
| 10 | 11° | Kodachrome8mmfilm | |
| 12 | 12° | 11 | Gevacolor8mmreversalfilm |
| 16 | 13° | 11 | Agfacolor8mmreversalfilm |
| 20 | td>14° | 16 | AdoxCMS20 |
| 25 | 15° | 22 | OldversionAgfacolor,Kodachrome25 |
| 32 | 16° | 22 | KodakPanatomic-X |
| 40 | 17° | 32 | Kodachrome40(movie) |
| 50 | 18° | 45 | FujiRVP(Velvia) |
| 64 | 19° | 45 | Kodachrome64,Ektachrome-X |
| 80 | 20° | 65 | IlfordCommercialOrtho | td>
| 100 | 21° | 90 | KodacolorGold,KodakT-Max(TMX),Provia |
| 125 | 22° | 90 | SvemaColor125,AstrumColorNegative125,IlfordFP4+,KodakPlus-XPan |
| 160 | 23° | 130 | FujicolorPro160C/S,KodakHigh-SpeedEktachrome |
| 200 | 24° | 180 | FujicolorSuperia200 |
| 250 | 25° | 180 | TasmaFoto-250 |
| 320 | 26° | 250 | KodakTri-XPanProfessional(TXP) |
| 400 | 27° | 350 | KodakT-Max(TMY),Tri-X400,IlfordHP5+ |
| 500 | 28° | 350 | |
| 640 | 29° | 560 | Polaroid600 |
| 800 | 30° | 700 | FujiPro800Z |
| 1000 | 31° | 700 | KodakP3200TMAX,IlfordDelta3200(seetextbelow) |
| 1250 | 32° | ||
| 1600 | 33° | 1400–1440 | Fujicolor1600 |
| 2000 | 34° | ||
| 2500 | 35° | ||
| 3200 | 36° | 2800–2880 | KodakT-Max(TMZ) |
| 4000 | 37° | ||
| 5000 | 38° | ||
| 6400 | 39° | ||
| 12800 | 42° | ||
| 25600 | 45° | ||
| 51200 | 48° | ||
| 102400 | 51° |
Oldscaleconversion
TheconversionbetweenASAandDINinthe1960sand70swasdifferentfromtoday.Thefigureshowsthescaleconversionin1952.Forexample,DIN21correspondstoASA80insteadofASA100.
Features
Thehigherthesensitivityspeed,thelargerthevalue.Inadditiontoshorteningtheexposuretime,italsohasanimpactonimagequality.Generallyspeaking,theimagequalityatlowsensitivityismoredelicateandthecolorsaremorefaithful.Whenthesensitivityishigh,therewillbenoiseandgrainproblems,makingthephotosmoreunbearabletozoomin.Whetheritisfilminthepastordigitalcamerastoday,thisphenomenonistrue.Especiallywhendigitalcamerasusehighsensitivity,theseverenoisegeneratedbyCMOSorCCDisevenmoreunbearablefortraditionalphotographers.Thisisoneofthereasonswhymanyphotographersstillchoosefilmcamerastoshoottheirworks.