HAND-HELD CAMERAS FOR AERIAL WORK
=Field of Use.=—The first cameras to be used for aerial photography were
hand-held ones of ordinary commercial types. Indeed the idea is still
prevalent that to obtain aerial photographs the aviator merely leans
over the side with the folding pocket camera of the department store
show window and presses the button. But the Great War had not lasted
long before the ordinary bellows focussing hand camera was replaced by
the rigid-body fixed-focus form, equipped with handles or pistol grip
for better holding in the high wind made by the plane's progress through
the air. Even this phase of aerial photography was comparatively
short-lived. The need for cameras of great focal length, and the need
for apparatus demanding the minimum of the pilot's or observer's
attention, both tended to relegate hand-held cameras to second place, so
that they were comparatively little used in the later periods of the
war.
Yet for certain purposes they have great value. They can be used in any
plane for taking oblique views, and for taking verticals, in any plane
in which an opening for unobstructed view can be made in the floor of
the observer's cockpit. They can be quickly pointed in any desired
direction, thus reducing to a minimum the necessary maneuvering of the
plane, a real advantage when under attack by “Archies” or in working
under adverse weather conditions.
For peace-time mapping work the hand-held camera, when equipped with
spirit-levels on top, and when worked by a skilful operator, possesses
some advantages over anything short of an automatically stabilized
camera. For experimental testing of plates, filters and various
accessories, the ready accessibility of all its parts makes the
hand-held camera the easiest and most satisfactory of instruments.
The limitations of the hand-held camera lie in its necessary restriction
to small plate sizes and short focal lengths, and in the fact that it
must occupy the entire attention of the observer while pictures are
being taken—the latter a serious objection only in war-time.
=Essential Characteristics.=—In addition to the general requirements as
to lens, shutter and magazine, common to all aerial cameras, the hand
camera must meet the special problems introduced by holding in the
hands, especially over the top of the plane's cockpit. An exceptionally
good system of handles or grips must be provided whereby the camera can
be pointed when pictures are taken, and held while plates are being
changed and the shutter set. The weight and balance of the camera must
be correct within narrow limits; the wind resistance must be as small as
possible; the shutter release must be arranged so as to give no jerk or
tilt to the camera in exposing.
As to the method of holding the camera, a favorite at first among
military men was the pistol grip, with a trigger shutter release (Fig.
37). Because of the size and weight of the camera the pistol grip alone
was an inadequate means of support and additional handles on the side or
bottom had to be provided for the left hand. Small (8 × 12 cm.) pistol
grip cameras were used to some extent by the Germans (Fig. 42), and a
number of 4 × 5 inch experimental cameras of this type were built for
the American Air Service (Fig. 37). But the grasp obtained with such a
design is not so good as is obtained with handles on each side or with
flat straps to go over the hands. The camera balances best with the
handles in the plane of the center of gravity. As to weight, no set
rules are laid down, but experience has shown that a fairly heavy
camera—as heavy as is convenient to handle—will hold steadier than a
light one. The American 4 × 5 inch cameras described below weigh with
their magazines in the neighborhood of twelve pounds.
[Illustration:
FIG. 37.—Pistol-grip aerial hand camera.]
=Representative Types of Hand-held Cameras.=—French and German hand-held
cameras are essentially smaller editions of their standard long-focus
cameras, and a description of them will apply to a considerable extent
to the large cameras to be discussed in a later chapter. The English and
American hand-held cameras are generally quite different in type from
the large ones, which are used attached to the plane.
[Illustration:
FIG. 38.—Diagram of French (deMaria) 26 cm. focus hand camera, using
13 × 18 cm. plates.]
_The French hand-held camera_ uses 13 × 18 centimeter plates, carried in
a deMaria magazine, and has a lens of 26 centimeters focus. The shutter
is the Klopcic self-capping type already described, and is removable.
The camera body, built of sheet aluminum, takes a pyramidal shape. In
Fig. 38, _A_ is the shutter release and _B_ the rectangular sight, of
which _C_ is the rear or eye sight. The complete sight may be placed
either on the top or on the bottom of the camera. At _D_ are the
handles, sloping forward from top to bottom; _E_ is a catch for holding
the magazine; _F_ is a door for reaching the back of the lens and the
lens flap; _G_ is a snap clasp for holding the front door of the camera
closed; _H_ is a ring for attaching a strap to go around the observer's
neck; _I_ is the lever which opens the flap behind the lens and releases
the focal-plane shutter; _J_ is a snap catch for holding the front door
of the camera open.
The operations with this camera are three in number. Starting
immediately after the exposure, the camera is pointed lens upward and
the plate changed by pulling the inner body of the magazine out and then
in; next the shutter is set; then the camera is pointed, and finally
exposed by a gentle pull on the exposing lever.
_The English hand-held camera_ (Fig. 186). This differs from the French
in the size of plate (4 × 5 inch), in the shape of the camera body,
which is circular, and in the type of shutter, which is fixed-tension
variable-opening. In the longer focus camera (10 to 12 inch) the shutter
is self-capping, and the aperture is controlled by a thumb-screw at the
side. In the smaller (6 inch) a lens flap is provided in front of the
lens and the shutter aperture is varied by a sliding saddle and cord.
The handles of the camera are placed vertical, instead of sloping as in
the French. The shutter is released by a thumb-actuated lever. Double
dark slides are used, as the multiple plate magazine has not found favor
in the English service.
_The German hand-held camera_ (Fig. 42). The German hand-held camera is,
like their whole series, built of canvas-covered wood, the body having
an octagonal cross-section. It is equipped with the Ica shutter and uses
the Ernemann six plate (13 × 18 cm.) magazine. The excellent system of
grips by which the camera is held and pointed is an especially
commendable feature. On the right-hand side is a handle similar to the
French type, but carefully shaped to fit the hand. The left-hand grip
consists of a long, rounded block of wood running diagonally from top to
bottom of the side, with a deep groove on the forward side for the
finger tips, while over the hand is stretched a leather strap, the whole
aim being to provide an absolutely sure and comfortable hold on the
camera during the plate changing and shutter setting operations.
[Illustration:
FIG. 39.—Front view of U. S. aerial hand camera, showing lens flaps
partly open, and details of tube sight.]
_United States Air Service hand cameras._ The hand camera developed for
the United States Air Service and manufactured by the Eastman Kodak Co.
is made in three models, using the bag magazine, a two-compartment
magazine, and roll film, respectively. The shutter is of the fixed (one
or two) aperture variable tension type, built into the camera. A
distinctive feature is the double lens flap, in front of the lens
actuated by the thumb pressure shutter release (Fig. 39). In the bag
magazine camera the shutter is set, as a separate operation, by a wing
handle, and a similar handle controls the tension adjustment. In the
two-compartment type (Fig. 33) the shutter wind-up is geared to the
plate changing lever, so that but one operation is necessary to prepare
the camera for exposure. In the film type (Fig. 34) a single lever
motion sets the shutter and winds up the film ready for the next
exposure. After the last exposure of all the film is wound backward on
its own (feeding) roller before removing from the camera. The film is
held flat by a closely fitting metal plate behind, and by guides at the
edges in front, an arrangement which with small sizes works fairly well
although the exquisite sharpness of focus attainable with plates is not
to be expected. The saving in weight made possible by the use of film in
place of plates in metal sheaths is about three pounds per dozen
exposures.
In all these cameras the sight—a tube with front and back cross wires—is
placed at the bottom. This position has been found the most convenient
for airplane work, as it necessitates the observer raising himself but
little above the cockpit, a matter of prime importance when the
tremendous drive of the wind is taken into account.