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ingenious devices have been invented for effecting the change (fig. 5). Some forms are effective and popular on account of their compactness and readiness for immediate exposure, but there is always a risk of the mechanism failing, and care has to be taken in charging them to lay the plates truly in their places. The very handy binocular cameras, or photo-jumelles, of which the “Verascope” (fig. 6) is a type, are of this class, and have additional

Fig. 7 -Beck’s Dai-Cornex Daylight-loading Camera.

magazines So also are hand cameras of R. and J. Beck’s “Frena” type, specially constructed for using stiff celluloid films. The films are notched on two sides and packed in bundles alternately with cards similarly notched. The pack of films and cards is placed in a magazine at the back of the camera, and by the movement of

Fig. 8—Watson’s “Vril” Camera.

a lever, after exposure, the exposed film and its following card are released, and by turning the camera down are dropped into a second receptacle. A “folding Frena” is now made as a folding camera with attached magazine for films, without which it can be used separately for plates. R and J. Beck’s new “Dai Cornex ” is a great improvement in this form of camera, being a daylight loading box magazine camera for plates, the plates being packed in a bundle of ridged sheaths, so that the are quite protected from light and can be put into or taken out of the camera in full daylight. In other respects it resembles other magazine cameras (fig. 7). Another useful magazine camera is the “Zambex,” carrying either plates or films, held in skeleton frames in envelopes which can be loaded or unloaded in daylight, and are kept ready for use in the back of the camera and exposed consecutively. For work in which

Fig 9.—Camera fitted with Twin Lenses, section to show working

A, Hood of finder.

B, Ground glass screen.

C, Mirror.

D, Viewing lens.

E, Working lens.

F, Shutter.

G, Focusing pinion

H, Plate carrier.

I, Plate.

speed is of primary importance hand cameras fitted with very rapid lenses and focal lane shutters are necessary and several forms of portable collapsible cameras of this kind are now available such as the Goerz-Anschutz Zeiss’s “Palmos” Watson’s “Vril” (fig. 8) Adams “Idento” &c. and are lighter and more portable than the reflex cameras. Hand cameras are generally fitted with screw-bushes for mounting on a tripod stand when time exposures are wanted. The light folding wooden or aluminium stands noted below are specially suitable

Twin lens and Reflex Cameras.—For photographing animals, objects in motion, public functions, &c., it is important to have the means of watching the movement till the critical moment of exposure arrives. For this it is convenient to have a camera fitted with twin lenses working in two separate compartments (fig. 9) or more simply with a mirror throwing a full-sized unreversed image of the object from the lens on to the focusing screen (fig. 10). With the former, which has the advantage that the image is seen before, during, and after exposure, the lenses must be of exactly equal focus and focused together by the same motion of the rack-work, the object being viewed on the focusing screen of the upper compartment, and the plate kept ready in the lower to be exposed when desired. Binocular hand cameras are also made on this principle, one compartment serving for focusing, the other holding lens and plates. Stereoscopic cameras are another form of twin-lens cameras, and are usually made for also taking single panoramic pictures.

In reflex cameras only one lens is necessary, though two are convenient, and can be used somewhat as in fig. 9. They generally consist of a cubical box camera containing a movable mirror facing the lens at an angle of 45° and throwing up the image projected from it on to a horizontal focusing screen, on which it is viewed through a flexible hood which folds down in the upper part of the camera when not in use (fig. 10). In order to get the greatest rapidity of exposure a focal-plane shutter is generally fitted, and by a single movement of the release the mirror is smoothly lifted and the plate exposed simultaneously. They should be fitted with an astigmatic lenses working at large apertures for very rapid work. In some forms the lens is fixed, but usually there is a front bellows extension for long-focus lenses, with rising and falling front, to which swing motion may be given, a swing-back not being generally used with the focal plane shutter. In the “Ernex” camera E. Human has made an arrangement by which the camera back, horizontal viewing screen and reflector are made to swin simultaneously, by a rack and pinion movement. They may also have reversing or revolving backs for quickly changing the position of the plate. 5 in. ✕ 4 in. and 31/4 in. ✕ 41/4 in. are the usual sizes of the plates, but larger and smaller sizes are also available. These cameras require the best workmanship and perfect mechanism for successful working and freedom from any jarring' movement in releasing the shutter or mirror. The focusing screen must also be in accurate register with the focus of the lens on the plate. Those forms in which the image can also be viewed at the height

Fig. 10-Reflex Camera,

A, Lens.

B, Mirror.

C, Ground-glass.

D, Plate

E, Supplementary mirror.

of the eye, as in the Graflex (fig. 10), are preferable. Although reflex cameras are rather heavy and bulky as hand cameras, they have many advantages over the ordinary hand camera with finder and focusing scales for the purpose of the press photographer, the naturalist and others, in observing and recording very rapid movements, and have come into very general use for such purposes. They permit the accurate focusing of a full-sized image on the ground glass up to the moment of exposure, especially useful when lenses of long or short focus are required and when the rising or swing front is in use. The aspect of this image on the ground-glass is also a great aid in the selection and placing of the subject and in judging the exposure required for it They practically have all the advantages of a stand camera and can be used as such on a stand for subjects requiring prolonged exposure. They are also coming into increasing use in studio work for portraits of children, &c. Their use and adjustments are discussed by G. E. Brown in the British Journal Almanac for 1909.

Panoramic Cameras.-Many so-called “panoramic” cameras have been introduced from time to time, among them T. Sutton’s (1861), and J. R. Johnson’s “Pantascopic” (1864), but did not

Fig. 11. Section of “Al-Vista” Panoramic Camera.

come into general use till the use of curved surfaces of celluloid film enabled such cameras of convenient size and weight to be put on the market. They are on the same principle as one made by F. von Martens in 1845 for curved daguerreotype plates, and covering an angle of 150°. P. Moessard’s “Cylindrographe” of 1889 was the first of the modern type. It consists of a semi-circular