For panoramic photography various special types of cam era have from time to time been introduced in order to satisfy the scientific require ment that, in covering the ab normally wide angles usually embraced in this kind of work, the lens should rotate on its nodal point of emergence. But practically all the earlier pan oramic cameras, an account of which was given in the B.J.A. of 1892, have disappeared, and even the interesting and effi cient little Panoram Kodak (fig. 24), which takes pictures on a section of roll film 34 in. x oi in. with a lens swinging on its own axis through the arc of a cir cle, has comparatively few users. A few professional panoramic cameras, such as the "Cirkut" and the "Korona"—the latter made by the Gundlach-Manhattan Optical Co. of Rochester, U.S.A.—are available. But in modern practice panoramic photographs are commonly made by exposing several plates to cover sections of the complete picture.
Special cameras for map reproduction—often of huge dimen sions—and for copying in connection with "process" work need not be specifically described as to all intents and purposes they are elaborations of the studio form. For Colour Photography (q.v.) various particular forms of camera and dark slide have been devised, more particularly in connection with the taking of the three negatives required for trichrome work on paper. The simplest method of obtaining the latter is separate exposure of three panchromatic plates in ordinary slides, the lens being screened successively by green, red and blue-violet filters. Greater speed is obtained by use of the Sanger-Shepherd repeating slide in which the three filters are placed immediately in front of sections of a long plate, the sections with their respective filters being exposed in quick succession by passing the slide along a frame fitted to the back of an ordinary camera. A modification of this repeating slide has been introduced by F. Newens and there have been more recent developments. A more elaborate system consists in obtaining the three negatives at a single exposure by means of a specially constructed camera in which the image transmitted by the lens is trebled by the addition of prisms, one image reaching its plate directly, the other two reaching theirs by reflection. Other devices accomplish the same result by different methods. In some colour cameras the prisms are re placed by a mirror system, a recent example of the latter type being the special Jos-Pe camera process.
However, at the time of writing it seems very highly probable that the various specialized forms of the one-exposure camera for all of the varied applications of colour-photography will within a brief period of time be rendered obsolete. This im portant change in the technical practice of colour-photography will be inevitably brought about by the notable improvements in the application of the tripack method. In this new technique a single simultaneous exposure is given to three films packed to gether. One of these films is green-sensitive, another is red
sensitive, while the third film is blue-sensitive. By this ingenious combination, which greatly simplifies the problem of taking colour-pictures, noteworthy practical advances may be confi dently expected throughout the entire field of colour-photography.
The construction of cameras for stereoscopic photography (q.v.) has reached a high degree of perfection in models such as the "Verascope" of J. Richard, the Leitz "Heidoscope" and the Voigtlander "Stereoflectoscope," the last two having a reflex finder in which a full size image is shown by a third lens (fig. 26).
In the practice of Photo-micrography likewise, a large choice of apparatus is available, ranging from cameras of very long extension with elaborate arrangements for securing correct align ment to simple attachments for use with ordinary cameras for low power work. In addition to horizontal apparatus some fine cameras have been designed by Zeiss and others to work vertically, while others can be used in conjunction with the microscope.
Although the subject of Colour Photography (q.v.) is dealt with elsewhere, reference should be made here to the multiple image optical system including the beam-splitter, for photograph ing plural images involved in stereoscopic and colour pictures. (See Abstracts Royal Photographic Society 1935.) Since Cinematography, Aerial and X-ray photography are dealt with separately, such apparatus is not discussed here.
Cinematography is dealt with under MOTION PICTURES (see especially MOTION PICTURE TECHNOLOGY by C. E. K. Mees). Aerial photography is treated under AERONAUTICS and AVIATION, also under SURVEYING. X-ray photography is discussed under X-RAYS ; X-RAYS AND CRYSTAL STRUCTURE and related subjects.
Enlargers.—The old method of enlarging by direct photog raphy with a short focus lens and an ordinary camera of long extension has for a number of years been largely discarded in favour of the employment of apparatus resembling the ordinary optical lantern. In the modern enlarger (fig. 25) a negative or a transparency takes the place of the lantern slide, the screen being represented by an easel to which a piece of bromide paper or a sensitive plate is, after focussing, affixed. A powerful beam of artificial light is passed, with the help of a condenser, through the negative or transparency and the enlarging lens with the result that an image is projected varying in enlargement according to the distances between the negative and the lens and between the lens and the sensitive surface of the paper or plate. The illumi nant may be either electric light or gas, but the former is now generally preferred, partly because it facilitates the construction of vertical enlargers which have some advantages over the hori zontal form. A number of automatic enlargers have been designed.