THE BRANCHES OF PHOTOGRAPHY Amateur Photography.—The use of photography for mak ing personal records has extended very greatly since portable cameras and sensitive materials were introduced, and the tendency is continually towards a simplification of the work to be done by the user and a diminution in the amount of expert knowledge re quired to get good results. This has resulted in the establishment of commercial firms to develop and print photographs made by the amateur, so that the great majority of photographs are now taken by those whose knowledge of the subject is limited to that necessary for making the exposures. The cameras used are chiefly of the folding type using a cartridge of film and are often of very small size. Many now use 35 mm. motion picture film.
The film can be loaded into the camera without the use of a darkroom and removed after exposure for development. For development, the films are hung by clips in deep tanks. They are printed by artificial light upon gas-light or developing-out papers, which are made in different degrees of contrast to suit the negatives obtained. As a general rule the photographic dealers will deliver prints from an exposed roll of film within two days. Enlargements are made upon bromide paper, fre quently by means of enlarging cameras in which the focus is automatically maintained correct while the scale of magnification is varied. (See Plate III., fig. 5.) In addition to roll films, films in packs are largely used, each separate unit having a tab of paper attached to it by which it can be withdrawn after exposure. A small number of amateur cameras still use plates or flat cut films in suitable holders.
Photographers who prefer to develop their own films usually employ a so-called "developing tank." (See Plate V., fig. 2.) The film is placed in a wooden changing box, in which it can be wound up with a light-tight flexible apron on to a spool. This spool to gether with the film is then transferred to a metal tank fitted with a light-tight lid, in which the film is developed.
When a darkroom is employed, the duration of development can be determined by one of three methods: (I ) By observation ; the development is carried on until the strength of the image is judged sufficient. This requires much experience and cannot be used with panchromatic materials.
(2) By factorial development ; this system was introduced by Alfred Watkins of Hereford, England. The number of seconds that elapse from immersion in the developer to the first appear ance of the image is noted. This time is then multiplied by a cer tain number called the "developing factor," to arrive at the total time of development. The factor depends upon the material used and the composition of the developer. The method gives good results in the hands of an experienced worker.
(3) Development for a fixed time at a definite temperature. This method possesses the maximum of advantage and reliability. It is always used when negatives are developed in tanks and has largely displaced the other methods.
Printing can be done either in a printing frame or with a small printing box in which the negative is placed on a sheet of glass, the paper placed on it, and a platen then brought down which secures contact and simultaneously lights an electric lamp under the negative. A grade of paper suitable to the contrast of the negative is chosen, and exposure is judged from the density of the negative.
Almost all the cameras used in amateur photography are de signed primarily for use in the hand and are only occasionally used upon tripods. In addition to the small portable cameras, many amateur photographers use reflex cameras and folding cameras fitted with focal plane shutters. (See PHOTOGRAPHY : Apparatus.) Advanced amateur photographers have contributed very much to the development of photography. They were among the first to employ colour sensitive plates, to use lenses of special types, such as telephoto or extremely wide aperture lenses, .to study the printing processes, and to develop the artistic use of photography. (See PHOTOGRAPHY : Pictorial.) Professional Photography.—The earliest photographic por trait appears to be the Daguerreotype taken of his sister by J. W. Draper of New York in 1840. The sitter was made up with white powder and photographed in full sunlight, an exposure of 5 minutes being given. The Daguerreotype process came into general use for portraiture, the plates being protected by glass in small leather cases, and these represented the common form of portraiture until the wet collodion process was introduced in 1851.