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
magazines.
Fig. 7.—Beck’s Dai-Cornex Daylight-loading Camera.
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 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 they 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.
Fig. 8.—Watson’s “Vril” Camera.
For work in which speed is of primary importance hand cameras fitted with very rapid lenses and focal plane shutters are necessary and several forms of portable collapsible cameras of this kind are now available such as the Goerz-Anschütz 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.
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| Fig. 9.—Camera fitted with Twin Lenses, section to show working. |
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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
anastigmatic 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,
Fig. 10.—Reflex Camera.
a, Lens.
b, Mirror.
c, Ground-glass.
d, Plate.
e, Supplementary mirror.
horizontal viewing screen and reflector are made to swing 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
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.
Fig. 11.—Section of “Al-Vista” Panoramic Camera.
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
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. Moëssard’s “Cylindrographe” of 1889 was the first of the modern type. It consists of a semi-circular
