the history and practice of the art of photography-第9章

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eful　to　see　that　the　slightest　particle　be　removed；　for　the　act　of　inserting　the　plate…holder　will　set　it　in　motion；　if　left；　and　cause　those　little　black　spots　on　the　plate；　by　which　an　otherwise　good　picture　is　spoiled。　　The　camera　should　be　so　placed　as　to　prevent　the　sun　shining　into　the　lenses。

In　taking　portraits；　the　conformation　of　the　sitter　should　be　minutely　studied　to　enable　you　to　place　her　or　him　in　a　position　the　most　graceful　and　easy　to　be　obtained。　　The　eyes　should　be　fixed　on　some　object　a　little　above　the　camera；　and　to　one　sidebut　never　into；　or　on　the　instrument；　as　some　direct；　the　latter　generally　gives　a　fixed；　silly；　staring；　scowling　or　painful　expression　to　the　face。　Care　should　also　be　taken；　that　the　hands　and　feet；　in　whatever　position；　are　not　too　forward　or　back　ward　from　the　face　when　that　is　in　good　focus

If　any　large　surface　of　white　is　present；　such　as　the　shirt　front；　or　lady's　handkerchief；　a　piece　of　dark　cloth　（a　temporary　bosom　of　nankeen　is　best；）　may　be　put　over　it；　but　quickly　withdrawn　when　the　process　is　about　two　thirds　finished。

A　very　pleasing　effect　is　given　to　portraits；　by　introducing；　behind　the　sitter；　an　engraving　or　other　pictureif　a　painting；　avoid　those　in　which　warm　and　glowing　tints　predominate。　The　subject　of　these　pictures　may　be　applicable　to　the　taste　or　occupation　of　the　person　whose　portrait　you　are　taking。　This　adds　much　to　the　interest　of　the　picture；　which　is　otherwise　frequently　dull；　cold　and　inanimate。

Mr。　J。　H。　Whitehurst　of　Richmond；　Va。；　has　introduced　a　revolving　background；　which　is　set　in　motion　during　the　operation；　and　produces　a　distinctness　and　boldness　in　the　image　not　otherwise　to　be　obtained。　The　effect　upon　the　background　of　the　plate　is　equally　pleasing；　it　having　the　appearance　of　a　beautifully　clouded　sky。

In　practising　Photographic　drawing　on　paper；　the　student　must　bear　in　mind　that　it　is　positively　essential；　to　secure　success　in　the　various　processes；　to　use　the　utmost　precaution　in　spreading　the　solutions；　and　washes　from　the　combination　of　which　the　sensitive　surfaces　result。　　The　same　brush　should　always　be　used　for　the　same　solution；　and　never　used　for　any　other；　and　always　washed　in　clean　water　after　having　been　employed。　Any　metalic　mounting　on　the　brushes　should　be　avoided；　as　the　metal　precipitates　the　silver　from　its　solution。　The　brushes　should　be　made　of　camels　or　badger's　hair　and　sufficiently　broad　and　large　to　cover　the　paper　in　two　or　three　sweeps；　for　if　small　ones　be　employed；　many　strokes　must　be　given；　which　leave　corresponding　streaks　that　will　become　visible　when　submitted　to　light；　and　spoil　the　picture。

These　few　preliminary　hints　and　suggestions；　will；　I　trust；　be　of　some　service　to　all　who　adopt　this　pleasing　art　as　a　profession；　and　will；　with　a　due　attention　to　the　directions　given　in　the　practical　working　of　the　Daguerreotype；　Calotype；　etc。；　ensure　a　corresponding　measure　of　success。



CHAP。　V。

DAGUERREOTYPE　APPARATUS。


The　entire　Daguerreotype　process　is　comprised　in　seven　distinct　operations；　viz：

1。Cleaning　and　polishing　the　plate。

2。Applying　the　sensitive　coating。

3Submitting　the　plate　to　the　action　of　light　in　the　camera。

4。Bringing　out　the　picture；　in　other　words　rendering　it　visible。

5。Fixing　the　image；　or　making　it　perminentso　that　the　light　may　no　longer　act　upon　it。

6。Gilding：　　or　covering　the　picture　with　a　thin　film　of　gold　which　not　only　protects　it；　but　greatly　improves　its　distinctness　and　tone　of　color。

7。Coloring　the　picture。

For　these　various　operations　the　following　articles　which　make　up　the　entire　apparatus　of　a　Daguerrean　artist　must　be　procured

1。THE　CAMERA。（Fig。　5。）。　The　Camera　Obscura　of　the　Italian　philosophers；　although　highly　appreciated；　on　account　of　the　magical　character　of　the　pictures　it　produced；　remained　little　other　than　a　scientific　toy；　until　the　discovery　of　M。　Daguerre。　The　value　of　this　instrument　is　now　great；　and　the　interest　of　the　process　which　it　so　essentially　aids；　universally　admitted。　A　full　description　of　it　will　therefore　be　interesting。　　＇hipho_5。gif＇

The　camera　is　a　dark　box　（a）；　having　a　tube　with　lenses　（b）　placed　in　one　end　of　it；　through　which　the　radiations　from　external　objects　pass；　and　form　a　diminished　picture　upon　the　ground　glass　（g）　placed　at　the　proper　distance　in　the　box　to　receive　it；　the　cap　c　covering　the　lenses　at　b　until　the　plate　is　ready　to　receive　the　image　of　the　object　to　be　copied。

Thus　a　（fig。　6。）　representing　the　lens；　and　b　the　object　desired　to　be　represented；　the　rays　（c；　c）　proceeding　from　it　fall　upon　the　lens；　and　are　transmitted　to　a　point；　which　varies　with　the　curvature　of　the　glass；　where　an　inverted　image　（d）　of　b　is　very　accurately　formed。　At　this　point；　termed　the　focus；　the　sensitive　photographic　material　is　placed　for　the　purpose　of　obtaining　the　required　picture。

The　great　disideratum　in　a　photographic　camera　is　perfect　lenses。　They　should　be　achromatic；　and　the　utmost　　＇hipho_6。gif＇　transparency　should　be　obtained；　and　under　the　closest　inspection　of　the　glass　not　the　slightest　wavy　appearance；　or　dark　spot　should　be　detected；　and　a　curvature　which　as　much　as　possible　prevents　spherical　aberration　should　be　secured。　The　effect　produced　by　this　last　defect　is　a　convergence　of　perpendiculars；　as　for　instance；　two　towers　of　any　building；　would　be　represented　as　leaning　towards　each　other；　and　in　a　portrait　the　features　would　seem　contracted；　distorted　and　mingled　together；　so　as　to　throw　the　picture　out　of　drawing　and　make　it　look　more　like　a　caricature　than　a　likeness。　If　the　lens　be　not　achromatic；　a　chromatic　aberration　takes　place；　which　produces　an　indistinct；　hazy　appearance　around　the　edges　of　the　picture；　arising　from　the　blending　of　the　rays。

The　diameter　and　focal　length　of　a　lens　must　depend　in　a　great　measure　on　the　distance　of　the　object；　and　also　on　the　superficies　of　the　plate　or　paper　to　be　covered。　　For　portraits　one　of　1　1/2　inches　diameter；　and　from　4　1/2　to　5　1/2　inches　focus　may　be　used；　but　for　distant　views；　one　from　2　inches　to　3　inches　diameter；　and　from　8　to　12　inches　focal　length　will　answer　much　better。　　For　single　lenses；　the　aperture　in　front　should　be　placed　at　a　distance　from　it；　corresponding　to　the　diameter；　and　of　a　size　not　more　than　one　third　of　the　same。　A　variety　of　movable　diaphrams　or　caps；　to　cover　the　aperture　in　front；　are　very　useful；　as　the　intensity　of　the　light　may　be　modified　by　them　and　more　or　less　distinctness　and　clearness　of　delineation　obtained。　These　caps　alway　come　with　Voitlander　instruments　and　should　be　secured　by　the　purchaser。

Though　the　single　acromatic　lens　answers　very　well　for　copying　engravings；　taking　views　from　nature　or　art；　for　portraits　the　double　should　always　be　used。　　The　extensive　manufacture　of　the　most　approved　cameras；　both　in　Europe　and　in　this　country；　obviates　all　necessity　for　any　one　attempting　to　construct　one　for　their　own　use。　　Lenses　are　now　made　so　perfect　by　some　artisans　that；　what　is　called　the　〃quick　working　camera〃　will　take　a　picture　in　one　second；　while　the　ordinary　cameras　require　from　eight　to　sixty。

The　camera　in　most　general　use　is　that　manufactured　by　Voitlander　and　Son　of　Germany。　　Their　small　size　consists　of　two　seperate　acromatic　lenses；　the　first；　or　external　one；　has　a　free　aperture　of　1　1/2　inches；　the　second；　or　internal；　1　5/8　inches；　and　both　have　the　same　focus；　viz：　　5　3/4　inches。　The　larger　size　differs　from　the　smaller。　　The　inner　lens　is　an　achromatic　3　1/4　inches　diameter；　its　focal　length　being　30　inches。　　The　outer　lens　is　a　meniscusthat　is　bounded　by　a　concave　and　convex　spherical　surface　which　meethaving　a　focal　length　of　18　inches。　　For　every　distant　view；　the　aperture　in　front　is　contracted　by　a　diaphram　to　1/8　of　an　inch。　By　this　means　the　light　is　reflected　with　considerable　intensity　and　the　clearness　and　correctness　of　the　pictures　are　truly　surprising。

THE　AMERICA　instruments　are　constructed　on　the　same　principle　and　many　of　them　are　equally　perfect。　　Mr。　Edward　Anthony　of　205　Broadway；　New　York　city；　has　constructed；　and　sold　cameras　fully　equal　to　the　German　and　for　which　Voitlander　instruments　have　been　refused　in　e