THE MOVING-PICTURE CAMERA AND ITS MECHANISM
The cinematograph camera differs entirely from the instruments used
in other branches of photography. While the advanced worker and
the prosperous picture-play producer employ costly and elaborate
machines, the amateur, or the independent worker, in the particular
field which he has selected for his operations, can get equally good
results with an apparatus only a fifteenth or even a twentieth part
as expensive. The range of operation with the cheaper instrument may
be limited, and it may be deficient in those many little refinements
which are characteristic of the professional appliance, and may lack
silver-plated finish and highly-polished woodwork or morocco leather
covering. But the camera itself is more important than these.
The cameras, both expensive and low-priced, work upon the same
fundamental principles. In the latter everything is reduced to the
simplest form so as to be readily and easily understood by the
beginner. They have the additional recommendation that the risk of
breakdown is eliminated, because the few essential component parts
are substantially made, well-proportioned, and nicely-balanced.
Serviceability and reliability are the outstanding features of the
low-priced camera, and it is applicable to almost every branch of the
craft.
Contrary to general belief, taking the "movies" is quite as simple as
snap-shot photography with a Kodak. In the latter case you press the
button; in the former you turn the handle; the camera does the rest.
The rotation of the handle, a simple operation, performs every duty
through the internal mechanism. It swings the shutter across the lens,
moves the film intermittently through the instrument, and coils up the
exposed film in its dark box.
As has been explained, the beginner is now able to make his selection
from a wide variety of makes, ranging in price from £5 ($25) upwards.
If one desires to gain experience in the cinematographic art with the
minimum capital outlay, the Jury, "New Era," or "Alpha" cameras will
suit the purpose excellently. Both are first-class, well-made machines,
having perfect registration and alignment, extremely simple and easy
to handle. The first-named model, which is the cheapest, is contained
in a mahogany case measuring 9-1/2 inches square by 4-3/4 inches deep,
and in the unloaded condition weighs 5-1/2 pounds. The "Alpha," which
costs a little more, is full value for money, and is well worth the
slightly increased price. This camera is fitted with a light-proof
hinged front panel giving access to the adjustable shutter, which
permits the opening of the latter to be varied within wide limits and
thus enables extremely rapid movements to be photographed while running
the machine at the normal speed. The spool boxes carry 100 feet of film
of standard gauge in each instance, and for general all-round work,
such as the recording of topical events, either model will be found
perfectly efficient. It may be mentioned that both models are supplied
without the lens, because the average beginner in motion-picture work,
having practised still-life or snap-shot photography, has usually
developed a marked fancy for some particular make of lens--Dallmeyer,
Cooke, Ross, Zeiss-Tessar, or Voigtlander. Naturally, being familiar
with the working of his favourite and knowing what he can do with
it, he feels more at home when he is able to have it fitted to his
moving-picture machine. Here, again, there is a wide selection to meet
all purses, so that the most fastidious tastes in regard to the lens
may be gratified. On the other hand, if the beginner has no marked
preference, and wishes to be economical, he can get a lens capable of
doing first-class work at a remarkably low price. His complete outlay
upon the camera and the lens need not exceed £6 5_s._, or, say, $31.
If prices are not to be so strictly considered, and if the beginner
wishes to have a machine of the finest type at a comparatively low
figure, he cannot do better than fit himself out with a Williamson
camera, the price of which, complete with lens, is £10 10_s._, say
$52. Except for an expert, it is difficult to detect the difference
between this machine and one which costs five times as much, for both
are designed upon the same lines, are equally well made, and equally
capable of doing the finest work. It must not be forgotten that Mr.
James Williamson, the designer of the latter instrument, was one of the
pioneers in cinematography, and, in his machine, the results of some
twenty-five years varied and accumulated experience are incorporated.
He has been able to realise just those essentials which are required
for a high-class apparatus free from complexity, and this end has been
achieved to excellent effect. The camera, finished in a brass-bound
mahogany or teak case--the latter is preferable for working in tropical
countries--measures 9-1/2 inches square by 4-3/4 inches deep, is fitted
with a Zeiss-Tessar 2-inch lens with focusing, and iris diaphragm.
It weighs 7-1/2 pounds complete in loaded condition. It is eminently
suited for all round duties, from the rush and tumble of topical work
to the uneventful, quiet but exacting requirements of the laboratory.
[Illustration: THE JURY MOVING-PICTURE CAMERA.
B. Driving sprocket. A, C. Upper sprocket pulleys. D. Exposure window.
H. Gate. E, F. Lower sprocket pulleys. G. Exposed film-box guide
pulley.]
[Illustration: THE WILLIAMSON TOPICAL CAMERA AND TRIPOD.
A. Camera. B. Handle. C. Lens. D. View finder. E. Tripod head. F.
Horizontal panoramic movement handle. G. Vertical panoramic movement
handle.]
These machines by no means exhaust the selection. Other manufacturers
have produced very good instruments at competitive prices, but those
which I have mentioned represent probably the best in their respective
classes. For the purpose of introduction to the art of cinematography
the beginner can do no better than obtain one of them. If, after a
little experience, he comes to the conclusion that he has ventured into
the wrong province, then his monetary expenditure is not serious.
It will be seen that the aspirant has no lack of inducement to embark
upon the moving-picture industry. Provided he has acquired a certain
knowledge of the elements of photography, and is possessed of average
intelligence, there is no reason why he should not be able to produce
pictures with his inexpensive machine that are in all ways comparable
with the product of the professional worker and the costly instrument.
Naturally, as the intricacies of the craft are mastered, the tyro will
wish for a more elaborate apparatus. He can gratify his ambitions in
accordance with his progress, or with the improvement in his financial
position.
The mechanism of the modern cinematograph camera is very simple in
its character and very easy to understand. The necessary parts are
very few in number. In all cameras the chief object is to effect
the forward intermittent movement of the film at regular intervals
and for a defined distance. For this purpose the early types of
camera were fitted with what is known as the Geneva stop movement.
Opinion is divided upon its merits, some authorities condemning it
unequivocally, while others uphold it strenuously, contending that it
gives a steadier and freer motion. There is much to be said in favour
of the latter view. Mechanically the Geneva stop movement is perfect.
So far as cinematography is concerned its advantages were proved most
emphatically by Mr. Robert Paul, the first man to bring motion pictures
into commercial application in Great Britain. He adopted this movement
in his camera, and it cannot be denied that his pictures were in every
way equal to those produced to-day, while his camera has never been
excelled. Curiously enough, although this movement has been superseded,
there is a tendency among expert workers to revive it, and many cameras
specially built have been fitted with it.
The movement more commonly used is that known as the "claw." It is
simple, and has the advantage of bringing the film into place for an
exposure with a sharp, quick jerk. But it is a movement which requires
to be designed very finely in order to perform its work smoothly and
evenly, and without inflicting any injury upon the film.
The claw consists of a small lever in duplicate, which is so mounted
as to have an eccentric movement and is driven direct by the main gear
wheel rotated by the handle. The free upper end of each arm of the
lever has a projecting pointed tooth of sufficient size to engage with
the perforations on either side of the film. With the revolution of the
wheel upon which it is mounted eccentrically the claw engages with the
perforations, and, thus gripping the film after the manner of a ratchet
and pawl, jerks it downwards a definite distance. When this downward
movement is completed the claw disengages from the perforations and
falls back clear of the film. Then the wheel, continuing its rotary
movement, proceeds to lift the claw. When it has raised it to its
highest point it brings it forward smartly to re-engage with the
perforations, and causes a fresh downward movement of the film.
The action is intermittent and occurs at regular intervals, while
the movement of the film is always the same. Quick engagement and
disengagement of the perforations is imperative for preventing the
vibration and tearing of the film.
[Illustration: Fig. 1.--Mechanism of camera showing threading
of film.]
The mechanism of the camera may be understood from the diagram (Fig.
1), which refers to the Williamson instrument. The sprocket A is driven
directly by the operating handle, which engages with the sprocket
spindle. This sprocket A is fitted with two rows of teeth, mounted
upon its periphery, and so spaced apart, both circumferentially
and transversely, as to coincide with the distances between the
perforations of the film. A pair of twin rollers, D and E, bear against
this sprocket under the tension of a spring, their object being to
keep the film pressed firmly against the sprocket. The teeth engage
with the film perforations, so that by the rotation of the handle and
sprocket the film is fed forwards regularly, smoothly and evenly, as it
is drawn from the loaded spool box B.
The film is brought into position before the lens by passing through
what is known as the "gate." This device H consists of two parts of
which the first is fixed irremovably while the second is hinged to the
first at one side and kept flat against it by means of a spring. Both
of the parts are provided with an aperture or window, the exact size of
a cinematograph picture--1 inch wide by 3/4-inch deep--through which
the light passes, after admission through the lens, to strike upon the
sensitized surface of the film. There is just sufficient space between
the two parts of the gate to permit the film to move easily, and its
object is to hold the film perfectly flat and steady during the period
of exposure. Each picture is thus kept in absolute focus.
The feed through the gate is accomplished by the claw N, which is
mounted upon the eccentric O as already described. At the instant of
exposure the claw is free of the film, or in the "out position," as it
is termed, so that the sensitized ribbon is absolutely still. When an
exposure has been made, the claw, having risen to the highest point
of its travel, re-engages with the film and jerks it down 3/4 inch,
so as to bring a fresh unexposed surface before the lens. As the film
emerges from the gate it is picked up once more by the sprocket A, the
engagement of the perforations in the film with the sprocket teeth
being assured by the two rollers J and K. The film then passes under
the guide roller L, and is wound up on the bobbin M in the exposed
film box C, the bobbin being worked through the handle that drives the
mechanism.
The rotation of the handle also ensures, through gearing, the
revolution of the shutter P, whereby the lens is eclipsed
intermittently. The shutter is a ring fitted with an opaque sector
which comes before the lens and shuts out the light during the movement
of the film through the gate H by the claw N. In the Williamson camera
this shutter is recessed into the case.
Although the lens may be of the fixed focus class--the focussing
distance varying with the stop used--focussing can be carried out
independently if very critical work is required. In the case of the
Williamson camera and others of this type, focussing is accomplished
by opening the shutter and the side of the camera and looking through
the gate. In some cameras a focussing tube is provided. This passes
from the gate to the rear of the instrument, through a space provided
between the superimposed film dark-boxes. It is telescopic at the
forward end. Thus, when focussing is being carried out, it can be
extended so as to come flush with the gate, and pushed back out of the
way when all is ready for working, so that the free movement of the
film is not obstructed in any way. The rear end of the tube, which
extends through the rear face of the camera box, is fitted with a cap
to save the film from being fogged by light entering from behind.
One conspicuous advantage of the Williamson machine is that the whole
of the mechanism is mounted upon a skeleton casting fixed to the
interior of the mahogany case by means of four screws. By withdrawing
these the whole of the internal mechanism may be removed intact, and
much trouble is saved when inspection or repairs are necessary.
In some cameras the intermittent movement of the film is effected by a
single claw which engages with the perforations upon one side of the
film only. But this movement is not perfect. All the pulling strain
is thrown upon one side of the film. This gives it a tendency to move
unevenly into the gate and also increases the risk of tearing.
The driving gear of the camera is so adjusted that one complete
revolution of the handle completes eight exposures. Consequently two
revolutions have to be made per second to maintain the necessary speed
of sixteen pictures per second. In the Williamson camera this is
emphasised as a fixed speed in ordinary working, and any compensations
demanded by the varying intensity of the light are made by altering the
aperture of the lens. This is a logical method, for if the operator is
required to make such compensations by varying the speed of his handle
he is apt to obtain an indifferent result. It requires a very skilled
operator indeed to vary the speed of the handle with judgment between
the narrow limits possible. In some cameras this compensation for light
is effected by varying the area of the opaque section of the shutter,
but this is not so simple or effective a method as the variation of the
stop. The latter can be accomplished while the camera is being driven,
but in the former it is necessary that the work should be stopped while
the front panel camera is opened and the shutter adjusted.
As for the tripod, one cannot be too careful in choosing it. This
apparently insignificant detail has a far-reaching effect upon the
picture results. Any ordinary tripod used in photographic work may
suffice, but its absolute rigidity is essential. A tight head, too, is
most necessary, without which the operator will get a side-to-side
sway upon the picture. It must be borne in mind that in turning the
handle there is a tendency, especially at first, to exert an unequal
pressure upon the handle side of the camera, and, unless the support
and its head are kept absolutely rigid, the pictures will betray
evidences of the defect. The telescopic ladder tripod is very handy for
topical work. This, when it is extended and when the camera is fixed,
brings the lens some 7 feet above the ground. A cross-rail placed from
12 to 25 inches above the ground, and attached to the rear legs, offers
a platform upon which the operator can stand to work his instrument. In
this way both camera and operator are brought above the heads of the
crowd, and an uninterrupted view can be obtained.
For moving-picture work a special type of tripod head has been evolved,
which allows the camera to be moved bodily through both the horizontal
and the vertical planes while exposures are being made. Thus it
can follow a subject travelling in either of these directions. The
movements are upon the rack and pinion principle, a small handle being
fitted to each motion so that either can be operated independently of
the other. By means of this panoramic attachment the main object in the
picture, such as a carriage or an aeroplane, may be followed in either
direction. But if both movements are to be completed simultaneously,
the operator will require help. One person must sight the object and
keep it in the picture by the manipulation of the two handles governing
the respective movements of the tripod head, while the other confines
his energies to turning the camera handle.
Although the moving-picture camera is built substantially and strongly,
its mechanism is comparatively delicate. While it will withstand the
hardest descriptions of legitimate work, it succumbs readily to brutal
treatment. Although operated by means of a handle, it is neither a
coffee mill nor a barrel organ, but a sensitive scientific instrument,
and it must be treated as such if the finest results are to be
obtained. Rough usage will throw out the registration and alignment. If
handled carefully a camera should perform its task for years without
needing repair. The effects of wear and tear can be mitigated very
appreciably by keeping the moving parts well lubricated with good oil,
such as is used for clocks, which neither gums nor clogs the bearings,
nor injures the mechanism in any way.