THE MOVING PICTURE CAMERA, ITS CONSTRUCTION, AND OPERATION
Although it was as far back as 1894 that the first commercial moving
picture camera appeared in Great Britain, the years have not produced
many marked departures from the design as elaborated by Paul. Time has
proved his plan to be the most reliable and efficient. But as the art
has developed and many minds have been concentrated upon the apparatus,
it has undergone modification and improvement in minor details, all
tending towards greater excellence in the ultimate results.
Paul’s camera was a small wooden cabinet, measuring only about six
inches each way. It contained merely the requisite intermittent
mechanism to bring successive depths of the film before the lens, and
the tube to enable focussing to be carried out easily from the back,
and in such a way that it was impossible for the film to become fogged
when the tube was left open inadvertently.
This instrument was a model of simplicity, compactness, portability
and convenience. The film was carried in separate dark boxes of a size
to hold 160, 350, or 700 feet, according to requirements. These were
detached from the camera itself, the box of unexposed film slipping
into a device on top of the camera in such a way as to ensure a
light-tight joint, and locked into position to prevent accidental
detachment. From this box the film was led through the camera
mechanism, past the lens and into a second box, similarly detachable.
The apparatus therefore was resolved into three main parts--the camera,
and the unexposed and exposed film boxes.
The modern cinematograph camera is completely self-contained; the film
boxes are incorporated within the case that carries the mechanism for
moving the film forward. Further improvement is hard to imagine. Bulk
and dimensions are reduced to the minimum, with, at the same time, the
maximum of efficiency.
The cinematograph camera, unlike most machinery, is called upon to
face exigencies, and to perform exceedingly hard work under the most
adverse conditions. To-day it may be in the broiling sun on a tropical
desert; a few weeks hence it is plunged into the extreme cold of the
Arctic circle; a little later it is well-nigh submerged in a reeking
swamp or vapour bath. Such varying conditions subject the material and
workmanship of the instrument to a supreme ordeal. Consequently the
greatest care has to be exercised in the selection of material, the
fashioning of the component parts, and their fitting together. Only
the best seasoned mahogany can be utilised to withstand the strains of
warping, shrinking, and expansion under extremes of heat and cold, and
climatic fluctuations.
In the ordinary stand camera used for still-life work, there is a
bellows which can be racked to and fro to enable the subject to be
focussed sharply upon the ground glass screen. The cinematograph camera
has no bellows, and there is no fixed screen for focussing purposes. In
the simpler and cheaper cameras, suited to amateur use, the operator is
not troubled with focussing details at all, the lens being of a fixed
focus as in certain types of snap-shot hand cameras; but in the more
expensive instruments, designed for producing the finest classes of
work, focussing facilities are incorporated.
In order to grasp the operation of the camera, we will open the hinged
door with which it is provided on one side, and gain access to its
interior mechanism. It would be invidious to select any special type of
camera, inasmuch as they all work more or less upon the same principle,
the differences being only in minor details.
By reference to the illustration it will be seen that the apparatus is
in three main parts. The rear half of the cabinet carries two square
compartments, _A_ and _B_, one above the other. These are for the two
film boxes, _A_ carrying the unexposed, and _B_ the exposed film. It
will be noticed that the cinematograph works upon the system of roller
photography. Indeed, it might be described almost as a semi-automatic
application of the familiar snap-shot camera using roll-films.
[Illustration: THE FILM-MOVING MECHANISM OF A CINEMATOGRAPH CAMERA.
The spool of unexposed film is carried in dark box A. From this it
is led over sprocket D, through the “gate” between the lens and the
focussing tube C, where it is exposed. The film is then jerked down the
depth of a picture through the gate by claws F, over sprocket and into
exposed film box B, where it is wound on a bobbin. E is the eye-piece
of the focussing tube.]
The lens is set centrally in the front face of the camera, and carries
a screw, by means of which focussing is effected by moving the lens
itself to and fro a short distance within a horizontal tube, which
corresponds to the bellows in the ordinary camera. In addition it
is fitted with stopping facilities working upon the well-known Iris
principle, whereby the size of the aperture may be increased or
diminished by a rectilinear movement. Behind the lens, and on a line
with it in the interior, a tubular connection _C_ extends transversely
through the width of the camera to the rear, and through the outer wall
to the external face of the case. This is the focussing tube, into
which the operator looks through the small circular orifice _E_ in the
back face of the camera, known as the eye-piece.
The mechanism by which, with an intermittent motion, the film is
jerked forward three-quarters of an inch after each exposure, is of
the simplest design. The film as it issues through a narrow slit from
the unexposed film box _A_, is passed under a small guide roller,
having a smooth face. Thence it passes upwards over a second roller
and down under the sprocket wheel, the teeth of which engage with the
perforations in the edges of the film, and thus guide it forward. As
the film passes upwards from the sprocket wheel, it is kept in mesh by
another guide roller, which maintains an easy pressure upon the film to
keep it in contact with the wheel, this grip being ensured under the
tension of a spring. The roller is mounted on the end of a small lever,
which can be moved slightly so as to release the grip upon the sprocket
wheel in order to insert the film. The arrangement adopted enables the
contact roller to ride over any variations in the thickness of the
films should such exist--a remote possibility in view of the wonderful
mathematical accuracy with which the films are made to-day. It is
impossible for the film to jump the sprocket wheel, even when the
machine is run at a very high speed. The contact roller is so mounted,
however, that it offers no resistance to the free passage of the film.
The film now passes behind the lens for exposure, travelling through
what is known as the “gate,” which consists of two parts, one fixed and
rigid, the other having a slight swinging movement. By means of the
gate the film is guided evenly into position, and held rigidly behind
the lens during exposure. The swinging part of the gate is clamped to
the fixed section by means of a spring catch, so that when the gate
is closed the film is imprisoned between two sheaths which hold it
firmly, and keep the surface flat and even during exposure. The end of
the focussing tube _C_ presses against the moving part of the gate and
tends to hold it rigid.
The film is pulled through the gate by an ingenious plan. There are
two claws or hooks _F_, the points of which engage with a perforation
on either side of the film. These two fingers are controlled by an
up-and-down cam movement attached to the bottom sprocket. As the latter
revolves, the hooks are lifted and carried upward. Reaching the limit
of their upward travel, they drop upon the film, clutching it by the
perforations, and as the claw action has a sharp downward movement,
the gripped film is pulled down suddenly and smartly through the gate
three-quarters of an inch at a time. The extent of the downward travel
reached, the claws are lifted so as to disengage with the film, are
swung upwards once more, and the same cycle of operations is repeated
until the whole length of film has been exposed.
After the exposure is made, the film passes downwards and through
mechanism which is almost a duplicate of that immediately above the
lens. It passes under the rocking contact roller, which keeps the
perforations meshed with the teeth on the sprocket wheel, after
passing round which it continues under a guide roller, and enters the
lower film box _B_, where it is wound on a bobbin.
Action is imparted by the rotary movement produced by the turning
of the handle through suitable mechanism, which is carried in a
small space on the opposite side of the camera to that containing
the film. The handle, however, not only supplies the drive to the
intermittent film moving action, but also rotates the shutter steadily
and continuously, through gearing. The shutter is mounted in a small
special compartment behind the lens and in front of the film. It is
adjustable; that is, the opaque sector can be increased or reduced
in area so as to increase or diminish the size of the opening; thus
the period of exposure can be varied according to the light, and as a
supplement to the stopping down of the lens. The gearing is practically
the same in all English cinematograph cameras, namely, 8 to 1, and
the turning speed should be two revolutions per second, which is
practically the slowest speed permissible.
The preparation of the camera for exposure is as follows. The operator
has selected his working position, and the camera has been set up
rigidly and firmly on its tripod, so that no oscillation can occur
during exposure. The side of the camera is opened, and the loaded
film box, from the slit in the bottom of which the end of the film
protrudes, is slipped into the upper compartment.
Next the subject is focussed. The eye-piece of the focussing tube
is made telescopic, as a rule, so that it can be extended a slight
distance from the back face of the camera case to facilitate focussing;
it is fitted invariably with a light-tight screw cap or gravity fall
shutter, which closes over the eye-piece so that no light may enter
through the tube to fog the film. For focussing purposes a piece of
transparent film with a rough “Matt” surface is used. This is inserted
in the film gate to act in the same way as the ground glass screen in
the ordinary stand camera. The object is focussed by turning the screw,
which racks the lens forward or backward as desired. When the picture
appears sharp and clearly defined the matt film is removed, the cap is
replaced on the eye-piece, and the latter is pushed home flush with the
surface of the wood casing.
The film is now threaded. It will be observed that a slight loop is
made at either end of the gate. This is necessary in order to give
sufficient play to the film to enable the latter to be jerked down
without any strain with each movement of the hook-claws behind the
lens. If it were pulled directly off the top sprocket the film would
be torn. The loops are kept constant, the upper being connected to the
lower sprocket through mechanism so that they revolve simultaneously.
Consequently three-quarters of an inch of film is fed into the top loop
gate at the same time as three-quarters of an inch of film is jerked
through the lower side of the gate.
In loading, care must be taken that the sensitised surface is brought
towards the lens, and that the object is not taken through the
thickness of the celluloid base. In order to thread the film through
the gate the focussing tube is pushed back slightly--it is made
telescopic for the purpose--the spring catch of the gate is released,
and the moving part swung back. The film is now slipped into the
gate, care being taken to see that the hooks of the device whereby
it is intermittently pulled down after each exposure engage with the
perforations. The gate is now closed, and the focussing tube under the
action of a spring returns to its original position. Finally the film
is led into the unexposed film box, where it is secured by a clip to
the spindle of the reel. The box is shut, the handle is given a turn
to make sure that the mechanism runs evenly and smoothly, and then the
camera is closed, all being ready for taking the pictures.
There is a popular impression that the operation of the cinematograph
camera is as simple as turning a coffee-mill or a barrel-organ, and
that the cinematographer has nothing else to do but to revolve the
crank. Never was there a greater fallacy.
[Illustration: PAUL’S COMPLETE DEVELOPING, PRINTING AND DRYING OUTFIT.]
[Illustration: THE FIRST DEVELOPING ROOM IN GREAT BRITAIN, AT ROBERT
PAUL’S PIONEER FILM MANUFACTORY.
_See page 77._
]
Turning the handle appears remarkably easy at first sight, but a short
trial proves that appearances are deceptive. It is essential that
the handle should be rotated at uniform speed, and occasionally it is
no easy matter to resist the desire to slow down. For instance, when
a funeral is passing, there is an almost irresistible inclination to
slacken speed. The amateur responds to this desire, and is astonished
at the dislocated character of his pictures when projected upon the
screen. As a matter of fact, the slowest funeral procession has to be
taken with the same number of revolutions per second, and the same
number of exposures--sixteen pictures per second--as an express train
travelling at 60 miles an hour; the crawl of the tortoise has to be
photographed just as rapidly as a horse race, in order to secure
natural motion. If a subject has been photographed too slowly it cannot
be corrected by accelerating the speed in projection. The judgment of
the actinic value of the sunlight, and the requisite stop for the lens,
as well as the adjustment of the shutter, are factors which only can be
determined from experience.
[Illustration: AFTER DEVELOPMENT AND WASHING THE FILMS WERE TRANSFERRED
FROM THE RACKS TO THE CYLINDERS.]
[Illustration:
[_Photos by permission of Robert Paul._
THE DRYING ROOM, SHOWING FILMS WOUND ON THE DRYING DRUMS.
_See page 77._
]
Possibly the box _A_ contains a roll of film measuring 300 feet,
whereas the subject photographed only demands the exposure of 60 or 100
feet. Then one makes a few punch marks on the film by the manipulation
of a small brass knob projecting from the outside of the camera, and
marked “film punch.” When the film reaches the developing room, the
operators working in the ruby light can tell by these marks the ends of
a series of exposures.
When the upper box has been exhausted of film, the lower box, now
charged with exposed film, is removed, the empty upper box is slipped
out of its compartment and re-inserted into the lower recess, to serve
in turn as a receptacle for film after exposure, and a fresh loaded
film-box is placed in the upper space, the mechanism being threaded
as before. The operator can ascertain at a glance how much film still
remains to be used, because on the outside of the case is a dial which
registers in feet the amount of film exposed, and which is set to zero
whenever a fresh box of film is inserted.
The task of the operator is increased in difficulty where the subject
being taken is moving at great speed horizontally and vertically at
the same time, when the object passes in a very short while beyond the
field of the lens, and in order to secure a good record the operator
must follow the movements steadily and smoothly in such a way as to
keep the object near the centre of the picture. The development of
aviation has taxed the capabilities of the cinematographer to a supreme
degree; for in photographing moving objects in the air the camera has
to be trained in two directions at the same time.
For this work a special tripod is required. It has a flat table, but by
means of two gear wheels the camera can be swung round panoramically,
that is, in a horizontal direction, while another wheel will move it
up or down through as large a vertical arc as required. Rigidity and
freedom from oscillation are essential to secure sharp, well-defined
pictures, and consequently this moving table has to be of massive
construction, while the worm and wheel gearing has to be heavy to
ensure steady movement. The camera is fitted with a direct view finder,
whereby the operator can train his instrument so as to keep the subject
well in the picture. Both horizontal and vertical training movements
are carried out by means of hand-wheels.
One of the finest examples of the operator’s skill that I have ever
seen was a film of Wilbur Wright’s flying exploits in France, on the
occasion of his first visit to Europe. The camera was manipulated
by two men. One concentrated his energies on the revolution of the
photographing handle, while the other, with his eyes glued to a special
direct view-finder devised for this particular operation, kept the
camera steadily and regularly trained both horizontally and vertically
upon the aviator as he described his evolutions in the air. Their joint
efforts were so successful that they produced a film free from that
dislocated or jerky action which as a rule characterises the lateral
or vertical movement of the camera while exposures are being made; the
results were just as if the camera had been kept stationary during the
whole time.
The ordinary tripod is used generally for outdoor work. Many American
and Continental film producers, however, resort to a special type of
support for the camera in the studio or for indoor operations, such
as the filming of plays. This is a solid metal pillar, recalling a
machine-gun mounting, fitted with wheels to facilitate movement from
point to point, and other adjusting devices. It is an excellent support
for indoor work, as it ensures a solid foundation for the camera, free
from vibration. In many instances the camera is driven by an electric
motor.
It is sometimes desirable to secure two negative records of an
important event or subject, so that, should one film prove defective,
the mechanism break down, or the film be damaged or destroyed, the
duplicate is available and prevents a total loss. For this purpose the
camera is in duplicate, though contained within a single case, with two
lenses mounted side by side as in a stereoscopic camera. Both sets of
mechanism are operated by the single handle, and one person suffices
for the operation of the instrument.
Within a few years, cinematography has widened its sphere of usefulness
in a novel and unexpected way. Forty years ago no expedition of
importance set out without some member who possessed artistic ability,
that pictorial records of the life and character of the new country
might be brought back to civilisation. As photography developed, the
artist of palette and brush was superseded by a man armed with a
camera. To-day the latter gives way in his turn to the cinematographer,
who brings back to us marvellous animated pictures of the remote and
unknown corners of the globe.
An ingenious camera has been devised for this especial field of
enterprise. It contains a unique feature that had not been previously
applied to the art. Two investigators, Newman and Sinclair, by dint
of considerable experiment and labour, have succeeded in producing
a moving-picture camera with a reflex attachment, and this without
increasing the size of the case, or interfering with the action of
the short-focus lenses. By means of this apparatus focussing can be
accomplished in fifteen seconds, without disturbing the film in the
gate, which is threaded up, ready for use, before the camera is taken
from the dark room. In this way the camera can be operated in much
less time than is possible by means of the ordinary cinematographic
apparatus.
As may be seen from the diagram, Fig. 6, the internal mechanism of this
handy little camera differs radically from the description given in
the first part of the present chapter. The two film boxes are placed
side by side instead of one above the other. The film goes into and
out of them through narrow mouths, which, when the camera is closed
and light-tight, are automatically increased in size to facilitate the
passage of the film, and automatically decreased again when the camera
is re-opened. In order to see, arrange, and focus the picture, it is
only necessary to raise a knob on the top of the camera, which renders
the image visible by means of a magnifying eye-piece without disturbing
the film. The shutter is also adjusted from the outside of the camera,
and can be closed to give an exposure of 1/100th of a second.
[Illustration: FIG. 6.--THE NEWMAN-SINCLAIR REFLEX MOVING PICTURE
CAMERA.]
This camera is one of the most compact, portable, and lightest
cinematograph instruments yet evolved for the purposes of hard work.
It is designed to carry either 400 or 500 feet of film, and, when a
picture is finished, the end of the subject on the film is indicated
by a device which cuts a tongue-shaped opening in the film, and which
can be readily detected by touch when the film is uncoiled in the
dark room. It is an ideal instrument for travellers, explorers,
scientists, and others to whom quick work is imperative. Its many
excellent qualities received recognition from Captain R. Scott, R.N.,
who included it in the scientific equipment for the latest British
Antarctic expedition.
For special work, the usual form of camera is altered in certain
details, or equipped with special devices. Such modification is
emphasised particularly for the purpose of taking trick pictures, to
which subject reference is made in subsequent chapters.