In the "Sybils" (fig. 2o) of the first named firm extra rigidity is secured by a neat and effective "lazy-tongs" method of extension. Another representative model of this type is the Sinclair "Una" which, while less compact than the "Sybil," is sufficiently portable and only a trifle less efficient than the "square form." The "Sanderson" of the Houghton-Butcher Co. is remarkable for the length of its extension, the latitude of its rising, falling, and swinging front movements, and the ingenious provision made for the use of very short focus lenses.
Collapsible hand cameras are largely used for Press photog raphy. They form a type apart of which the Goerz-Anschiitz was the pioneer model. A typical modern camera of this class is the Ross "Panros" (fig. 2r) which is not only extremely convenient for hand work but can be so effectively used on a stand that it was adopted by the Royal Engineers for the field equipment of their Printing Companies, by whom it was extensively employed in the World War. Cameras of this kind are fitted with focal plane shutters (see p. 828) and very rapid lenses, f/4.5 being a usual aperture. In the "Ermanox" made by the Zeiss Ikon Co. an Ernostar anastigmat working at f.1.8 has been fitted with which instantaneous photographs can be secured in a theatre with ordinary stage lighting.
Magazine cameras in which a number of plates or films are packed and brought forward successively for exposure, some what on the principle of the changing-box, are now compara tively seldom used. Unless of the simplest construction, in which case they are bulky, the changing mechanism is apt to give trouble. Binocular and twin-lens cam eras represent an endeavour to provide the operator with a view of the object up to and includ ing the moment of exposure. They are literally, as their name implies, combinations of two sep arate cameras and two separate lenses, the focussing adjustments being correlated so that one half of the combination can be used for focussing, the other for exposing the plate. In the form of an inverted field glass, the focussing screen and the plate taking the place of the two eye pieces, binocular hand cameras are still to be met with, but the twin-lens, which in its later forms was an early "reflex," has been practically superseded by the single-lens reflex.
Modern reflex cameras form a class apart in connection with which much ingenuity of invention has been displayed and many patents have been taken out. The principle is explained in the
accompanying diagram (fig. 22) but, as in practice the reflex is usually held in the hand, it is now fitted with a collapsible vertical hood which enables the operator to look down through it on to the focussing screen. A second mirror can, if desired, be fitted in the hood for horizontal viewing, and focussing can be assisted by the use of a binocular focussing magnifier. Constructionally the reflex camera is a box containing a movable mirror interposed between the plate and the lens, and facing the latter at an angle of 45°. This throws up the image on to the horizontal focussing screen, on which it is viewed through the hood. The outstand ing mechanical feature of the re- ' Rex is the co-ordination of the movement of the mirror with the shutter release. The removal of the former to enable the image transmitted by the lens to reach the plate, and the instantaneous exposure of the latter by means of the shutter, are effected simul taneously. The shutter almost in variably fitted to these cameras is of the focal plane type, and more than a dozen models of re flexes by first-class makers are available. A typical pattern of the reflex camera, with movable mirror, horizontal focussing screen and viewing hood is the "Soho" by Kershaw and made by the Amalgamated Photographic Manu facturers, Ltd. (fig. 23). Reflex studios now take roll-film.
Reflex Camera and design and construction are considered by A. S. Newman in the Photographic Journal for 1921, p. The basic idea of the Roll-film camera has already been discussed. The folding Kodak (fig. 18) remains the most popular in strument of the type, and the latest models of it meet practi cally every need. Substantially the form has not altered although many new features are continually added. The metal door which closes the front of the camera falls down and forms a base board along which the panel carrying the lens, shutter and finder is drawn out until the required focussing adjustment has been made. In some models the fixed focus principle is applied; in others the focus can be altered, according to an affixed scale, to suit all distances from a few feet to infinity. Great clever ness has been displayed in ensuring the rigidity of both base board and lens panel. Focussing roll-film cameras, more or less closely resembling Kodaks, but containing various structural modifications, are now made by a number of firms.