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74 OV•TON.•N•) H•RrER, Bird . [Jan.Auk

BIRD PHOTOGRAPHY BY THE DIRECT PROCESS.

BY FRANK OVERTON• M.D. AND FRANCIS HARPER.

}VI•N¾ that show the home life of wild birds are objectsof great interestand , but and pictures fail to reveal the most striking of all the characteristicsof a bird -- its color. Photographyaffords an almostperfect means of record- ing other important characteristics,such as size, shape, and habi~ tat; but until recently it has been almosta total failure in record- ing the colorof the plumage. Hitherto the colorsof birds have been representedby meansof and their reproductionsor by means of hand-colored lantern slides. But bird-paintingis an extremelyslow and difficult process. The artists who are capable of adequately portraying birdsare surprisinglyfew in number,and to satisfactorilyreproduce the paintingson the printed pageis almostas difficultas to make the originalpictures. Consequentlymany of the printed pictures in colorare merely keys,and few paintedportraits, however pleas- ing their composition,are accuratein every particular. Hand- colored lantern slidesare valuable and beautiful, but most of them fail to representthe bird subjectsaccurately or in desirabledetail. Therefore, any additionalmeans of recordingvividly and minutely the natural colorsof wild birdsis worthy of carefulstudy. Sucha means is afforded by the use of the Lumi[re autochromeplates. Photographstaken upon these plates are transparencies,having the qualitiesof goodlantern slides,with the additionalquality of showingthe colorsin their natural tonesand in pleasingdetail. An autochromephotograph may be reproducedby engTaving and printing in the sameway that a may be reproduced. But an autochromeis much fuller of microscopicdetail than a painting done by hand, and this detail is too fine to be brought out by the engraver'sart at the presenttime. An autochrome, therefore, cannot be reproducedsatisfactorily upon the printed page unlessit happensto be made up of massesof color without Vol.1913 XXX] J 0VERTONANY HARrER, Bird Photography. 75 variegateddetail. But an autochromemay be usedas a lantern slide, and herein lies its greatest field of usefulness. It is more densethan an ordinary slide, but a good lantern will project an autochromephotograph upon the screenwith nearly all the bril- liancy that the plate exhibitswhen held in the hand and looked throughby daylight. The colorswill be slightlyaffected by the colorof the in the lantern,but not to a greaterdegree than the colorsof a paintingare affectedwhen seen in an artificiallight. An autochromeplate differsfrom an ordinaryphotographic plate chieflyin that a singlelayer of transparent,microscopical starch grains,dyed -,, and , and mixedin evenpro- portion, is interposedbetween the glassand the sensitivecoating or fihn. This coatingis extremelythin, and is madeof a panchro- matic emulsion. The plate is exposedin the camerawith the glass sidetoward the ,so that the rays of light must passthrough the coloredstarch grains before reachingthe emulsion. Each starch grainis about i of an inchin diameter. An autochromethus bearssome resemblance to a half-tone plate, but the dots upon it are only about one fifth as large as the smallestdots upon the best half-toneplate. The densityof the plate is due to the fact that the starch grains intercept a considerableamount of light. Any plate cameramay be usedin taking an autochrome,and a specialyellow screen, fitted to the lens,is the only extra pieceof apparatusneeded. If a screenis not used,the photographwill showa dominantpurplish tone, owingto the excessiveactinlsm of the violet and rays of ordinary light. The main difficultyof autochromephotography lies in the length of exposurerequired, which is 100 thnesas longas is necessaryfor an ordinary plate. This is owing to the absorptionof light rays by the colorscreen and by the coloredstarch grains. An auto- chromeof a wild bird is taken in the sameway that an ordinary negativewould be madeof the samebird, exceptthat the is greatly prolonged. The fastesttime in whichwe have taken a bird autochromeis one quarter of a second, which would corre- spondto •0-61 of a secondwith an ordinaryplate. On the other hand,a broodingBlue Jay in a dark thickethas posed for aslong as two minutes. The developmentof an autochromeis not especiallydifficult, 76 O,TERTONAND HARPER, Bird Photography. [Jan.[Auk although someexperience and skill are required to securethe best results. The factoffal method of Pontrolled-timedevelopment, 'asdescribed in the directionsaccompanying the plates,enables one to controlthe densityand contrastof the pictui'e. The formedby the first developmentof the plate is reversedin a reduc- ing solution,-and the plate is thereby converted from a into a positive. The first development, reversal of the image, seconddevelopment, and washing,may be completedin lessthan fifteen minutes,and the thin emulsionmay he dried in ten minutes more. An autochrome,therefore, possesses a still further advan- tage ox;era hand-coloredslide in the much shorter time required for its completion. An autochromeplate is a positive, and no satisfactorymethod has yet heen devised for nmking colored prints from it directly upon photographicpaper. It is well within the boundsof proba- bility, however,that experimentswhich are now being conducted in this direction may eventually be successful. Fortunately, any numberof duplicatesmay he made by photographingthe first plate upon other autochromeplates, in much the sameway that lantern slides are made by the use of a . The reproducedauto- chromesare not sobrilliant as the originals,but they may he shown with goodeffect in a lantern. We have taken several dozen bird authoehromesthat •nay be consideredsuccessful. The list includesthe Laughing Gull, Com- mon Tern, Black Skimmer, Bob-white, Fish Hawk, Flicker, Night- hawk, Blue Jay, Song Sparrow, Martin, Warbler, Catbird, Thrasher, and Robin. The number of our failures to securegood pictures has not exceededthe numberof our successes. Our experiencejustifies us in stating that the autochromemethod of photographyaffords a practical and definite meausof securing brilliant and useful photographsof normal wild birds in their natural hmmts, poses,and .