the history and practice of the art of photography-µÚ19ÕÂ
°´¼üÅÌÉÏ·½Ïò¼ü ¡û »ò ¡ú ¿É¿ìËÙÉÏÏ·ҳ£¬°´¼üÅÌÉ쵀 Enter ¼ü¿É»Øµ½±¾ÊéĿ¼ҳ£¬°´¼üÅÌÉÏ·½Ïò¼ü ¡ü ¿É»Øµ½±¾Ò³¶¥²¿£¡
¡ª¡ª¡ª¡ªÎ´ÔĶÁÍꣿ¼ÓÈëÊéÇ©ÒѱãÏ´μÌÐøÔĶÁ£¡
dry¡¡dip¡¡it¡¡into¡¡a¡¡solution¡¡of¡¡iodide¡¡of¡¡potassium£»¡¡containing¡¡five¡¡hundred¡¡grains¡¡of¡¡that¡¡salt¡¡dissolved¡¡in¡¡a¡¡pint¡¡of¡¡water¡£¡¡When¡¡perfectly¡¡saturated¡¡with¡¡this¡¡solution£»¡¡it¡¡should¡¡be¡¡washed¡¡in¡¡distilled¡¡water£»¡¡drained¡¡and¡¡allowed¡¡to¡¡dry¡£¡¡¡¡This¡¡is¡¡the¡¡first¡¡part¡¡of¡¡the¡¡process£»¡¡and¡¡the¡¡paper¡¡so¡¡prepared¡¡is¡¡called¡¡iodized¡¡paper¡£¡¡It¡¡should¡¡be¡¡kept¡¡in¡¡a¡¡port¡folio¡¡or¡¡drawer¡¡until¡¡required£º¡¡with¡¡this¡¡care¡¡it¡¡may¡¡be¡¡preserved¡¡for¡¡any¡¡length¡¡of¡¡time¡¡without¡¡spoiling¡¡or¡¡undergoing¡¡any¡¡change¡£
Mr¡£¡¡Cundell¡¡finds¡¡a¡¡stronger¡¡solution¡¡of¡¡nitrate¡¡of¡¡silver¡¡preferable£»¡¡and¡¡employs¡¡thirty¡¡grains¡¡to¡¡the¡¡ounce¡¡of¡¡distilled¡¡water£º¡¡he¡¡also¡¡adds¡¡fifty¡¡grains¡¡of¡¡common¡¡salt¡¡to¡¡the¡¡iodide¡¡of¡¡potassium£»¡¡which¡¡he¡¡applies¡¡to¡¡the¡¡marked¡¡side¡¡of¡¡the¡¡paper¡¡only¡£¡¡This¡¡is¡¡the¡¡first¡¡process¡£
Preparation¡¡of¡¡the¡¡paper¡¡for¡¡the¡¡Camera¡£The¡¡second¡¡process¡¡consists¡¡in¡¡applying¡¡to¡¡the¡¡above¡¡a¡¡solution¡¡which¡¡has¡¡been¡¡named¡¡by¡¡Mr¡£¡¡Talbot¡¡the¡¡¡¨Gallo¡Nitrate¡¡of¡¡Silver£»¡¨¡¡it¡¡is¡¡prepared¡¡in¡¡the¡¡following¡¡manner£º¡¡Dissolve¡¡one¡¡hundred¡¡grains¡¡of¡¡crystalized¡¡nitrate¡¡of¡¡silver¡¡in¡¡two¡¡ounces¡¡of¡¡distilled¡¡water£»¡¡to¡¡which¡¡is¡¡added¡¡two¡¡and¡¡two¡third¡¡drachms¡¡of¡¡strong¡¡acetic¡¡acid¡£¡¡¡¡This¡¡solution¡¡should¡¡be¡¡kept¡¡in¡¡a¡¡bottle¡¡carefully¡¡excluded¡¡from¡¡the¡¡light¡£¡¡¡¡Now£»¡¡make¡¡a¡¡solution¡¡of¡¡gallic¡¡acid¡¡in¡¡cold¡¡distilled¡¡water£º¡¡¡¡the¡¡quantity¡¡dissolved¡¡is¡¡very¡¡small¡£¡¡When¡¡it¡¡is¡¡required¡¡to¡¡take¡¡a¡¡picture£»¡¡the¡¡two¡¡liquids¡¡above¡¡described¡¡should¡¡be¡¡mixed¡¡together¡¡in¡¡equal¡¡quantities£»¡¡but¡¡as¡¡it¡¡speedily¡¡undergoe¡¡decomposition£»¡¡and¡¡will¡¡not¡¡keep¡¡good¡¡for¡¡many¡¡minutes£»¡¡only¡¡just¡¡sufficient¡¡for¡¡the¡¡time¡¡should¡¡be¡¡prepared£»¡¡and¡¡that¡¡used¡¡without¡¡delay¡£¡¡It¡¡is¡¡also¡¡well¡¡not¡¡to¡¡make¡¡much¡¡of¡¡the¡¡gallic¡¡acid¡¡solution£»¡¡as¡¡it¡¡will¡¡not¡¡keep¡¡for¡¡more¡¡than¡¡a¡¡few¡¡days¡¡without¡¡spoiling¡£¡¡A¡¡sheet¡¡of¡¡the¡¡iodized¡¡paper¡¡should¡¡be¡¡washed¡¡over¡¡with¡¡a¡¡brush¡¡with¡¡this¡¡mixed¡¡solution£»¡¡care¡¡being¡¡taken¡¡that¡¡it¡¡be¡¡applied¡¡to¡¡the¡¡marked¡¡side¡£¡¡This¡¡operation¡¡must¡¡be¡¡performed¡¡by¡¡candle¡¡light¡£¡¡¡¡Let¡¡the¡¡paper¡¡rest¡¡half¡¡a¡¡minute£»¡¡then¡¡dip¡¡it¡¡into¡¡one¡¡of¡¡the¡¡dishes¡¡of¡¡water£»¡¡passing¡¡it¡¡beneath¡¡the¡¡surface¡¡several¡¡times£»¡¡it¡¡is¡¡now¡¡allowed¡¡to¡¡drain£»¡¡and¡¡dried¡¡by¡¡placing¡¡its¡¡marked¡¡side¡¡upwards£»¡¡on¡¡the¡¡drying¡¡apparatus¡£¡¡It¡¡is¡¡better¡¡not¡¡to¡¡touch¡¡the¡¡surface¡¡with¡¡bibulous¡¡paper¡£¡¡It¡¡is¡¡now¡¡highly¡¡sensitive£»¡¡and¡¡ready¡¡to¡¡receive¡¡the¡¡impression¡£¡¡In¡¡practice¡¡it¡¡is¡¡found¡¡better¡¡and¡¡more¡¡economical¡¡not¡¡to¡¡mix¡¡the¡¡nitrate¡¡of¡¡silver¡¡and¡¡gallic¡¡acid£»¡¡but¡¡only¡¡to¡¡brush¡¡the¡¡paper¡¡with¡¡the¡¡solution¡¡of¡¡the¡¡nitrate¡£
Mr¡£¡¡Talbot¡¡has¡¡recently¡¡proposed¡¡some¡¡modifications¡¡in¡¡his¡¡method¡¡of¡¡preparing¡¡the¡¡calotype¡¡paper¡£¡¡¡¡The¡¡paper¡¡is¡¡first¡¡iodized¡¡in¡¡the¡¡usual¡¡way£»¡¡it¡¡is¡¡then¡¡washed¡¡over¡¡with¡¡a¡¡saturated¡¡solution¡¡of¡¡gallic¡¡acid¡¡in¡¡distilled¡¡water¡¡and¡¡dried¡£¡¡¡¡Thus¡¡prepared¡¡he¡¡calls¡¡it¡¡the¡¡io¡gallic¡¡paper£º¡¡it¡¡will¡¡remain¡¡good¡¡for¡¡a¡¡considerable¡¡time¡¡if¡¡kept¡¡in¡¡a¡¡press¡¡or¡¡portfolio¡£¡¡When¡¡required¡¡for¡¡use£»¡¡it¡¡is¡¡washed¡¡with¡¡a¡¡solution¡¡of¡¡nitrate¡¡of¡¡silver¡¡£¨fifty¡¡grains¡¡to¡¡the¡¡ounce¡¡of¡¡distilled¡¡water£©£»¡¡and¡¡it¡¡is¡¡then¡¡fit¡¡for¡¡the¡¡camera¡£
Exposure¡¡in¡¡the¡¡Camera¡£The¡¡calotype¡¡paper¡¡thus¡¡prepared¡¡possesses¡¡a¡¡very¡¡high¡¡degree¡¡of¡¡sensibility¡¡when¡¡exposed¡¡to¡¡light£»¡¡and¡¡we¡¡are¡¡thus¡¡provided¡¡with¡¡a¡¡medium¡¡by¡¡which£»¡¡with¡¡the¡¡aid¡¡of¡¡the¡¡photogenic¡¡camera£»¡¡we¡¡may¡¡effectually¡¡copy¡¡views¡¡from¡¡nature£»¡¡figures£»¡¡buildings£»¡¡and¡¡even¡¡take¡¡portraits¡¡from¡¡the¡¡shadows¡¡thrown¡¡on¡¡the¡¡paper¡¡by¡¡the¡¡living¡¡face¡£¡¡The¡¡paper¡¡may¡¡be¡¡used¡¡somewhat¡¡damp¡£¡¡¡¡The¡¡best¡¡plan¡¡for¡¡fixing¡¡it¡¡in¡¡the¡¡camera¡¡is¡¡to¡¡place¡¡it¡¡between¡¡a¡¡piece¡¡of¡¡plate¡¡glass¡¡and¡¡some¡¡other¡¡material¡¡with¡¡a¡¡flat¡¡surface£»¡¡as¡¡a¡¡piece¡¡of¡¡smooth¡¡slate¡¡or¡¡an¡¡iron¡¡plate£»¡¡which¡¡latter£»¡¡if¡¡made¡¡warm£»¡¡renders¡¡the¡¡paper¡¡more¡¡sensitive£»¡¡and¡¡consequently¡¡the¡¡picture¡¡is¡¡obtained¡¡more¡¡rapidly¡£
Time¡¡of¡¡Exposure¡£With¡¡regard¡¡to¡¡the¡¡time¡¡which¡¡should¡¡be¡¡allowed¡¡for¡¡the¡¡paper¡¡to¡¡remain¡¡in¡¡the¡¡camera£»¡¡no¡¡direct¡¡rules¡¡can¡¡be¡¡laid¡¡down£»¡¡this¡¡will¡¡depend¡¡altogether¡¡upon¡¡the¡¡nature¡¡of¡¡the¡¡object¡¡to¡¡be¡¡copied£»¡¡and¡¡the¡¡light¡¡which¡¡prevails¡£¡¡All¡¡that¡¡can¡¡be¡¡said¡¡is£»¡¡that¡¡the¡¡time¡¡necessary¡¡for¡¡forming¡¡a¡¡good¡¡picture¡¡varies¡¡from¡¡thirty¡¡seconds¡¡to¡¡five¡¡minutes£»¡¡and¡¡it¡¡will¡¡be¡¡naturally¡¡the¡¡first¡¡object¡¡of¡¡the¡¡operator¡¡to¡¡gain¡¡by¡¡experience¡¡this¡¡important¡¡knowledge¡£
Bringing¡¡Out¡¡the¡¡Picture¡£The¡¡paper¡¡when¡¡taken¡¡from¡¡the¡¡camera£»¡¡which¡¡should¡¡be¡¡done¡¡so¡¡as¡¡to¡¡exclude¡¡every¡¡ray¡¡of¡¡lightand¡¡here¡¡the¡¡dark¡¡slide¡¡of¡¡the¡¡camera¡¡plate¡¡holder¡¡becomes¡¡of¡¡great¡¡use¡¡bears¡¡no¡¡resemblance¡¡to¡¡the¡¡picture¡¡which¡¡in¡¡reality¡¡is¡¡formed¡£¡¡The¡¡impression¡¡is¡¡latent¡¡and¡¡invisible£»¡¡and¡¡its¡¡existence¡¡would¡¡not¡¡be¡¡suspected¡¡by¡¡any¡¡one¡¡not¡¡acquainted¡¡with¡¡the¡¡process¡¡by¡¡previous¡¡experiment¡£¡¡¡¡The¡¡method¡¡of¡¡bringing¡¡out¡¡the¡¡image¡¡is¡¡very¡¡simple¡£¡¡It¡¡consists¡¡in¡¡washing¡¡the¡¡paper¡¡with¡¡the¡¡gallo¡nitrate¡¡of¡¡silver£»¡¡prepared¡¡in¡¡the¡¡way¡¡already¡¡described£»¡¡and¡¡then¡¡warming¡¡it¡¡gently£»¡¡being¡¡careful¡¡at¡¡the¡¡same¡¡time¡¡not¡¡to¡¡let¡¡any¡¡portion¡¡become¡¡perfectly¡¡dry¡£¡¡¡¡In¡¡a¡¡few¡¡seconds¡¡the¡¡part¡¡of¡¡the¡¡paper¡¡upon¡¡which¡¡the¡¡light¡¡has¡¡acted¡¡will¡¡begin¡¡to¡¡darken£»¡¡and¡¡finally¡¡grow¡¡entirely¡¡black£»¡¡while¡¡the¡¡other¡¡parts¡¡retain¡¡their¡¡original¡¡color¡£¡¡Even¡¡a¡¡weak¡¡impression¡¡may¡¡be¡¡brought¡¡out¡¡by¡¡again¡¡washing¡¡the¡¡paper¡¡in¡¡the¡¡gallo¡nitrate£»¡¡and¡¡once¡¡more¡¡gently¡¡warming¡¡it¡£¡¡When¡¡the¡¡paper¡¡is¡¡quite¡¡black£»¡¡as¡¡is¡¡generally¡¡the¡¡case£»¡¡it¡¡is¡¡a¡¡highly¡¡curious¡¡and¡¡beautiful¡¡phenomenon¡¡to¡¡witness¡¡the¡¡commencement¡¡of¡¡the¡¡picture£»¡¡first¡¡tracing¡¡out¡¡the¡¡stronger¡¡outlines£»¡¡and¡¡then¡¡gradually¡¡filling¡¡up¡¡all¡¡the¡¡numerous¡¡and¡¡complicated¡¡details¡£¡¡The¡¡artist¡¡should¡¡watch¡¡the¡¡picture¡¡as¡¡it¡¡developes¡¡itself£»¡¡and¡¡when¡¡in¡¡his¡¡judgment¡¡it¡¡has¡¡attained¡¡the¡¡greatest¡¡degree¡¡of¡¡strength¡¡and¡¡clearness£»¡¡he¡¡shall¡¡stop¡¡further¡¡proceedings¡¡by¡¡washing¡¡it¡¡with¡¡the¡¡fixing¡¡liquid¡£¡¡Here¡¡again¡¡the¡¡mixed¡¡solution¡¡need¡¡not¡¡be¡¡used£»¡¡but¡¡the¡¡picture¡¡simply¡¡brushed¡¡over¡¡with¡¡the¡¡gallic¡¡acid¡£
The¡¡Fixing¡¡Process¡£In¡¡order¡¡to¡¡fix¡¡the¡¡picture¡¡thus¡¡obtained£»¡¡first¡¡dip¡¡it¡¡into¡¡water£»¡¡then¡¡partly¡¡dry¡¡it¡¡with¡¡bibulous¡¡paper£»¡¡and¡¡wash¡¡it¡¡with¡¡a¡¡solution¡¡of¡¡bromide¡¡of¡¡potassiumcontaining¡¡one¡¡hundred¡¡grains¡¡of¡¡that¡¡salt¡¡dissolved¡¡in¡¡eight¡¡or¡¡ten¡¡ounces¡¡of¡¡distilled¡¡water¡£¡¡The¡¡picture¡¡is¡¡again¡¡washed¡¡with¡¡distilled¡¡water£»¡¡and¡¡then¡¡finally¡¡dried¡£¡¡Instead¡¡of¡¡bromide¡¡of¡¡potassium£»¡¡a¡¡solution¡¡of¡¡hyposulphite¡¡of¡¡soda£»¡¡as¡¡before¡¡directed£»¡¡may¡¡be¡¡used¡¡with¡¡equal¡¡advantage¡£
The¡¡original¡¡calotype¡¡picture£»¡¡like¡¡the¡¡photographic¡¡one¡¡described¡¡in¡¡the¡¡last¡¡chapter£»¡¡is¡¡negative£»¡¡that¡¡is¡¡to¡¡say£»¡¡it¡¡has¡¡its¡¡lights¡¡and¡¡shades¡¡reversed£»¡¡giving¡¡the¡¡whole¡¡an¡¡appearance¡¡not¡¡conformable¡¡to¡¡nature¡£¡¡¡¡But¡¡it¡¡is¡¡easy¡¡from¡¡this¡¡picture¡¡to¡¡obtain¡¡another¡¡which¡¡shall¡¡be¡¡conformable¡¡to¡¡nature£»¡¡viz¡££»¡¡in¡¡which¡¡the¡¡lights¡¡shall¡¡be¡¡represented¡¡by¡¡lights£»¡¡and¡¡the¡¡shades¡¡by¡¡shades¡£¡¡It¡¡is¡¡only¡¡necessary¡¡to¡¡take¡¡a¡¡sheet¡¡of¡¡photographic¡¡paper¡¡£¨the¡¡bromide¡¡paper¡¡is¡¡the¡¡best£©£»¡¡and¡¡place¡¡it¡¡in¡¡contact¡¡with¡¡a¡¡calotype¡¡picture¡¡previously¡¡rendered¡¡transparent¡¡by¡¡wax¡¡or¡¡oil¡¡as¡¡before¡¡directed¡£¡¡Fix¡¡it¡¡in¡¡the¡¡frame£»¡¡Fig¡£¡¡29£»¡¡expose¡¡it¡¡in¡¡the¡¡sunshine¡¡for¡¡a¡¡short¡¡time£»¡¡and¡¡an¡¡image¡¡or¡¡copy¡¡will¡¡be¡¡formed¡¡on¡¡the¡¡photogenic¡¡paper¡£¡¡The¡¡calotype¡¡paper¡¡itself¡¡may¡¡be¡¡used¡¡to¡¡take¡¡the¡¡second£»¡¡or¡¡positive£»¡¡picture£»¡¡but¡¡this¡¡Mr¡£¡¡Talbot¡¡does¡¡not¡¡recommend£»¡¡for¡¡although¡¡it¡¡takes¡¡a¡¡much¡¡longer¡¡time¡¡to¡¡take¡¡a¡¡copy¡¡on¡¡the¡¡photogenic¡¡paper£»¡¡yet¡¡the¡¡tints¡¡of¡¡such¡¡copy¡¡are¡¡generally¡¡more¡¡harmonious¡¡and¡¡agreeable¡£¡¡After¡¡a¡¡calotype¡¡picture¡¡has¡¡furnished¡¡a¡¡number¡¡of¡¡copies¡¡it¡¡sometimes¡¡grows¡¡faint£»¡¡and¡¡the¡¡subsequent¡¡copies¡¡are¡¡inferior¡£¡¡This¡¡may¡¡be¡¡prevented¡¡by¡¡means¡¡of¡¡a¡¡process¡¡which¡¡revives¡¡the¡¡strength¡¡of¡¡the¡¡calotype¡¡pictures¡£¡¡¡¡In¡¡order¡¡to¡¡do¡¡this£»¡¡it¡¡is¡¡only¡¡nesessary¡¡to¡¡wash¡¡them¡¡by¡¡candlelight¡¡with¡¡gallo¡nitrate¡¡of¡¡silver£»¡¡and¡¡then¡¡warm¡¡them¡£¡¡¡¡This¡¡causes¡¡all¡¡the¡¡shades¡¡of¡¡the¡¡picture¡¡to¡¡darken¡¡considerably£»¡¡while¡¡the¡¡white¡¡parts¡¡are¡¡unaffected¡£¡¡After¡¡this¡¡the¡¡picture¡¡is¡¡of¡¡course¡¡to¡¡be¡¡fixed¡¡a¡¡second¡¡time¡£¡¡It¡¡will¡¡then¡¡yield¡¡a¡¡second¡¡series¡¡of¡¡copies£»¡¡and£»¡¡in¡¡this¡¡way£»¡¡a¡¡great¡¡number¡¡may¡¡frequently¡¡be¡¡made¡£
The¡¡calotype¡¡pictures¡¡when¡¡prepared¡¡as¡¡we¡¡have¡¡stated£»¡¡possess¡¡a¡¡yellowish¡¡tint£»¡¡which¡¡impedes¡¡the¡¡process¡¡of¡¡taking¡¡copies¡¡from¡¡them¡£¡¡In¡¡order¡¡to¡¡remedy¡¡this¡¡defect£»¡¡Mr¡£¡¡Talbot¡¡has¡¡devised¡¡the¡¡following¡¡method¡£¡¡¡¡The¡¡calotype¡¡picture¡¡is¡¡plunged¡¡into¡¡a¡¡solution¡¡consisting¡¡of¡¡hyposulphite¡¡of¡¡soda¡¡dissolved¡¡in¡¡about¡¡ten¡¡times¡¡its¡¡weight¡¡of¡¡water£»¡¡and¡¡heated¡¡nearly¡¡to¡¡the¡¡boiling¡¡point¡£¡¡The¡¡picture¡¡should¡¡remain¡¡in¡¡about¡¡ten¡¡minutes£»¡¡it¡¡must¡¡then¡¡be¡¡removed£»¡¡washed¡¡and¡¡dried¡£¡¡¡¡By¡¡this¡¡process¡¡the¡¡picture¡¡is¡¡re