Bichromate Methods Birds
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Bichromate Methods. Processes in which the material sensitive to light is an alkaline bichromate in contact with organic matter, such as gum, albumen, or gelatine. Most methods of photographic block and plate making come under this heading. (See Gum-bichromate, Carbon Printing, Artigue's Process, Photogravure, Collotype, Hydrotype, Aniline Processes, Fish Glue Process, etc.)
Biconcave. An optical term denoting that the two sides of a • lens are hollowed out. (See Lens.)
Biconvex. An optical term denoting that the two sides of a lens are bulged out. (See Lens.)
Binocular Camera. Another name for Stereoscopic Camera or for camera with twin lens finder.
Binocular Portraits or binographs. This term has been applied, to portraits in which the two elements of a stereogram are united in one picture ; or to pictures in which these two elements are united, and also all possible intermediate views of the object. The most simple and obvious means of producing a binograph is to rotate the camera in a horizontal plane during exposure ; the centre of rotation being at the distance of the principal object, and the amount of rotation must correspond to an angle, the chord of which is equal to the separation of the eyes. In the early days of photography great emphasis was laid on the artistic possibilities of binographic work, as it introduces unsharpness in much the same way as the eye sees (see J. Leighton's article, Photographic Journal^ May 20th, 1854, p. 211), and it is quite obvious that the principle is as applicable to landscape as to*portraiture. Examples of Binographic por-traits, and a full account of binography, will be found in The Amateur Photographer for July 26th, 1901 (p. 70 "to 73). Mr. Fred Boissonas, of Geneva, is the most notable advocate of binography at the present time.
Bioscope. See Cinematograph.
Birds, Photographing. See Animals, Photographing.