TodayI’mgoingtotalkabouttheinventionofthecameraandphotography.Thecameraisoftenthoughttobeamoderninvention.Butasearlyas1727aGermanphysicistdiscoveredthatlightdarkenedsilversaltachemicalcompound.Usin
TodayI’mgoingtotalkabouttheinventionofthecameraandphotography.Thecameraisoftenthoughttobeamoderninvention.Butasearlyas1727aGermanphysicistdiscoveredthatlightdarkenedsilversaltachemicalcompound.Usingasacameraabigboxwithasmallholetoletthelightinhemadetemporaryimagesonthesalt.Silversaltisstillthebaseoffilmtoday.
ThenaFrenchscientistmadethefirstpermanentpicturebyusingaspecialpieceofmetalsensitized（使…具感光力）withsilversalt.Aphotographhemadein1826stillexists.ThepainterDaguerreimprovedontheprocessbyplacingcommonsaltthekindweeatonthemetal.Thiswasin1839theofficialdateofthebeginningofphotography.
Buttheproblemwastheprintingofthephotographs.Anditwasnotuntilotherscientistsdevelopedthekindofpaperwenowusethatgoodprintingwaspossibleandphotographybecametrulycommon.Inthe1860sMathewBradywasabletotakehisfamouspicturesoftheAmericanCivilWarthusmakingportraitposesverypopular.
Inthe20thcenturyGeorgeEastmenoftheUnitedStatessimplifiedfilm-developingfilmandDr.EdwinLandinventedtheso-calledinstantcamerawithself-developingfilm.Ifwesaythatthephotographycameintoexistencein1839itfollowsthatithastakenmorethanonehundredyearsforthecameratoreachthepresentconditionoftechnicalrefinement（密度）.
56.Whatwasthebasisofphotography?
A.Theinventionofthecamera.
B.Thediscoverythatlightdarkenssilversalt.
C.Asmallboxwithaholetoletinlight.
D.Temporaryimagesmadebyascientist.
57.Howwasthefirstpermanentpicturemade?
A.Byplacingcommonsaltonaspecialpieceofmetaltocatchlight.
B.Byusingaverysmallandsimplecamera.
C.Byusingaspecialpieceofmetalsensitizedwithsilversalt.
D.Bymakingimagesonsilversalt.
58.Whatdoesthewriterregardastheofficialdateofthebeginningofphotography?
A.Theuseofcommonsaltintheprocessofmakingpictures.
B.ThefirstpermanentpicturemadebyaFrenchscientist.
C.ThetemporaryimagesonthesaltbyaGermanscientist.
D.Thefirstuseofsilversaltinmakingpictures.
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