This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Stereoscopic Camera. The stereoscopic camera in its simplest form consists of a partitioned box with a pair of perfectly matched lenses mounted on its front board in a fixed position. The lenses should be fitted with stereo shutters, both shutters acting simultaneously.
537. The camera should be equipped with a rising front; also a swing-back or swing-bed, in order that true and perpendicular lines may be obtained. A dividing partition inside of the camera will be necessary to prevent the images from fogging each other.
538. In Illustration No. 108 is shown a simple form of stereoscopic camera, size 5x7. It is equipped with a Wollensak shutter and symmetrically matched lenses. The camera possesses a swing for either back or bed, a removable front board, and a hooded, brilliant finder. The stereo division inside of the bellows is on an improved roller principle, and when the camera is closed or opened the division rolls and unrolls automatically. The stereo division can be detached from the camera at will, when it is desired to use the camera for taking 5x7 pictures instead of stereo pictures.
539. In Illustration No. 109 we present the Goerz-Anschiitz Folding camera, which is adapted to stereoscopic photography. This camera is provided with an adjustment by which the separation of the lenses can be varied - a point of some importance for the most accurate work. With this camera the stereoscopic division can also be removed and one of the lenses brought facing the center of the plate. By this means the camera which takes a plate 3 1/3 x 7 is rendered available for extensive panoramic views. Where it is intended to use the camera for both stereoscopic and panoramic view work, it should be fitted with anastig-mat lenses. They, having great covering power, may be used single or double. In Illustration No. 109a is shown a roll film Kodak constructed for stereoscopic work.
Commercial Outfit. To make a business of stereoscopic photography one should be equipped with a square-bellows stereo-camera, fitted with focal-plane, as well as between-the-lens, shutter, both arranged so that either may be used independent of the other. They should also be provided with lenses of different focal-lengths, from 3 1/2 to 10-inch focus, the latter to be used when working at great distance from the object and the former for working in confined places, interiors, etc.
Choice Of Lenses. Very good commercial work may be made with the ordinary rapid rectilinear lenses, using two 3 1/4 x 4 1/4 lenses for this purpose. Where the most accurate results are to be obtained, however, the corrected or anastigmat lenses should be employed, such as the Goerz Dagor f. 6.8; Bausch & Lomb Zeiss-Tessar 11b, speed f. 6.3; Dallmeyer Stigmatic Series II, speed f. 6; Ross Homocentric Series C, speed f. 6.3; Voigtlander Col-linear, Series III, speed f. 6.8, or Cooke Series III, speed f. 6.5. Any of these types of lenses are sufficiently rapid and may be used for speed work or time exposure.
542. These lenses are selected for their covering power, depth of focus, and relatively large working aperture. The smaller the working aperture of lenses the easier and more accurately can they be paired. Little or no difficulty is experienced, therefore, in matching lenses of the rectilinear type, while lenses having a speed of f. 6.8 or f. 6.3 must be selected with great care, and lenses having apertures of f. 5.5, f. 4.5, etc., are matched only with difficulty. In addition to this the depth of focus of the most rapid lenses is so very slight that they must be stopped down in actual practice so their theoretical speed is of no value and the length of required exposures is as great as lenses listed to work with a smaller aperture.