One of the largest industries in the world had developed from the invention of a scientific toy. The cinema camera, in addition to its entertainment value, is of incalculable service to the engineer and the scientist
THROUGH long ages “the twinkling of an eye” has served to denote the briefest space of time. The rapid flicker of an eyelid passes unnoticed by the eye. When a picture is thrown upon the screen or retina at the back of the eye the impression is conveyed by the optic nerve to the brain. With the closing of the lid, the picture is at once cut off from the retina, but the sense of seeing remains, and before this impression can disappear the lid has been raised again and sight is restored.
The phenomenon is known as “persistence of vision”, and this is the secret of the cinema. On this peculiarity of human sight is based one of the largest industries in the world. The patrons of the cinema are reckoned in their millions all over the world and the extent of the cinematograph’s influence on modern life cannot be estimated.
For over half a century the best brains of science and engineering-have striven to perfect the cinematograph. The range of the cinema is not limited to the presentation of drama and literature in pictorial form; even the educational and historical aspects do not represent the limits of its scope. The cinema camera and projector are of incalculable value to the engineer. A carefully designed mechanism may, for example, give unaccountable trouble when on test. A film of the apparatus in action is taken at the fastest possible speed by a cinematograph camera, and is then reproduced as slowly as possible by a projector. A study of the slow-motion picture generally reveals the defect.
INTERIOR OF AN EARLY FILM CAMERA, built by L. A. Augustin Le Prince. Le Prince’s first camera used sixteen lenses and two films. The camera illustrated is believed to be the first single-lens , cinematograph model ever built.
In a modern high-speed camera the film runs at 120 miles an hour and takes 3,000 pictures a second. A film in slow motion will reveal defects in the delicate synchronizing gear that permits a machine-gun to fire between the revolving propeller blades of fighting aircraft. The stream of bullets can be watched crawling across the screen with the propeller blades chopping the air between.
The same equipment will demonstrate what happens when a structural component is tested to destruction in one of the special machines designed for the purpose. When the engineer knows what part of the test specimen fails first he can modify and strengthen the design accordingly.
The cinematograph began, in common with many other revolutionary inventions, as a scientific toy. Once the underlying principle of its operation was discovered and its possibilities realized, development followed. There is, however, a long gap between the toy and the intricate devices of to-day. Photography, electricity, celluloid, the “magic lantern” — all had to be made known before that gap could be filled. The toy was, however, the starting point and it was suggested by the great astronomer Sir John Herschel in 1825.
Herschel demonstrated to his friend Charles Babbage that it was possible by spinning a coin on edge to see both sides of it at once. Babbage in turn mentioned the matter to Dr. Fitton, who in 1826 produced the toy known as the thaumatrope. Most people have early recollections of this device as the “wonder spinner”, consisting of a card with a string tied to either side. On one side of the card is drawn, say, a bird, and on the other an empty cage. When the card is twirled round by the strings the bird appears to be inside the cage. Both sides of the card (as with Herschel’s coin) are seen at once, as the eye, because of persistence of vision, is unable to separate the two pictures.
Within a few years the simple thaumatrope had been supplemented by a series of devices that brought the cinematograph a little nearer to realization. Ranking high among the early pioneers who worked on the fascinating-problem of the moving picture were Dr. Joseph Plateau of Ghent, and Dr. Simon Ritter von Stampfer of Vienna, who simultaneously invented the stroboscope about 1832. The modern stroboscope (which has no connexion with cinematography) is used for determining the speeds of reciprocating and of rotating parts in machinery. The apparatus of Plateau and von Stampfer consisted of a vertical disk capable of being revolved in front of a mirror. Figures were drawn or painted round the disk and between each pair of figures a slit was made in the edge of the disk. Viewed successively through the slits in the revolving disk the separate figures, drawn to represent various stages of movement, were blended into one picture that appeared to be moving.
FORERUNNER OF THE MODERN CINEMATOGRAPH CAMERA -Le Prince’s so-called single-lens model. One of the two lenses on the left served merely as a viewfinder. The contrast between early machines, such as this, and the modern cine-camera is a striking testimony to the rapid development of an epoch-making invention.
This device was followed at a later date by the zoetrope or “wheel of life”. This consisted of a shallow cylinder capable of being revolved on a pivot. The sides of the cylinder were pierced by vertical slots and inside was arranged a series of drawings depicting motion, such as a dog running. When the cylinder was revolved the succession of pictures, viewed in turn through the slots, appeared as one moving picture. Variations of this device had mirrors to give a better result. Among these was the praxinoscope, in which the pictures were reflected on to a polygonal mirror inside the cylinder. In the thaumatrope and in the more elaborate devices that followed it, the picture was intermittently obscured from sight. This intermittence is man’s mechanical contribution to cinematography, the counterpart of Nature’s “persistence of vision”. Without intermittence there would lie no opportunity for Nature to play her part in deceiving the eye, and the result would be a blur across the screen similar to the “invisible” spokes of a fast revolving wheel. Intermittence is ensured by a revolving shutter that obscures the camera or projector lens while the substitution of one picture for the next is being made.
None of the early devices could be regarded except as a toy or a scientific novelty. They were not capable of recording or of reproducing events that had taken place. The discovery of photography, however, paved the way for further developments in the making of moving pictures, and in 1872 the first continuous photographic record was made. This was the famous experiment carried out in California by an Englishman named Muybridge.
Experiment with 24 Cameras
Muybridge arranged some two dozen cameras in a row at a little distance from a whitewashed fence. Every camera was provided with a shutter which was actuated by the pulling of a string. The strings were led from the cameras across the intervening space to the fence. A horse then galloped alongside the fence, breaking the strings in succession. A series of photographs was thus taken showing the animal in the various positions of its gallop. Apart from its value in the development of the cinematograph, Muybridge’s experiment clearly demonstrated that a horse does not gallop with its legs extended “fore and aft”, the traditional representation in old sporting prints.
Muybridge made further experiments in the photography of moving objects, and at the same time investigation was being undertaken by the French experimenter Marey. Muybridge used a single camera and lens and arranged a number of plates round a revolving disk. Later Marey used a roll film on a paper base, but this was not entirely successful.
In 1887 L. A. Augustin Le Prince built a camera in Paris. It is now preserved in the Science Museum at South Kensington, London. The camera was equipped with sixteen lenses for recording photographs on two films mounted side by side on rollers. The films consisted of sensitized gelatine and the rollers were accommodated in a wooden box attached to the back of the camera.
The lenses were fitted with shutters worked by electro-magnets which were released in quick succession by the turning of a rotary switch. Eight lenses were first used on one film and the remaining eight were then directed on to the other film. The second film came into action while the first was being made ready to receive another series of eight pictures. While exposures were being made the film was momentarily clamped by a cam-operated frame. A number of photographic records were made by this machine, which was used also as a projector for throwing the pictures on to a screen. With the introduction of the celluloid roll film in 1889 by George Eastman, the future of the cinematograph was assured.
Edison, the famous inventor, then took a hand in the development of the cinematograph. From 1887 to 1889 Edison had worked on the production of a moving-picture machine that would work with his newly invented phonograph. Here was the idea underlying the modern talking film.
In August 1889 Edison was first able to use the Eastman film and two months later he demonstrated the “kinetoscope”, in which pictures taken by his “kinetograph”, or motion-picture camera, were viewed by the aid of a magnifying lens. Edison introduced a projector also for his pictures, but this was not put on the market. Edison’s apparatus provided for a width of film of 35 millimetres, and this is now the standard throughout the world for professional work.
While Edison was conducting his experiments in America, William Friese-Greene was working on the perfection of the cinematograph in England. In 1888 he made a photographic film on paper made transparent by soaking in castor oil.
In the following year Friese-Greene produced the first celluloid cinematograph film, showing a scene at Hyde Park Corner, London, and this was exhibited on a screen at Chester in 1890. Friese-Greene held the master patent covering the modern motion picture. As with many an inventor before him, he did not live to reap any reward from the work that has proved of such benefit to millions of people.
The cinematograph camera and projector had thus been brought to a commercial standard of efficiency by the beginning of the present century, and improvements have followed in rapid succession. The modern motion-picture camera is a marvel of scientific and engineering development, but in general the simple principles laid down by the early pioneers have not been supplanted.
As in an ordinary camera, the lens and the light-tight compartment behind it are all-important. Mounted on the camera are two flat circular magazines, one containing a roll of film. The other, at the beginning of a “take”, is empty. From the full magazine the film is passed partly round a sprocket wheel, whose teeth or prongs engage with the perforations on either side of the celluloid strip.
Electric Power Units
The film then enters a gate behind the lens and is pulled through by a claw device that engages with the perforations. The action of the claw mechanism is intermittent so that the film stops for a moment in the gate while an exposure is made through the lens. Between the brief pauses of the film in the gate, movement is masked by a revolving shutter synchronized with the winding mechanism. After having left the gate the film again passes close to the sprocket wheel and then enters the second magazine.
HIGH-SPEED CAMERA for slow-motion photography. The film travels through this camera at a speed of 120 miles an hour from spools rotating at 15,000 revolutions a minute. When films taken by this camera are projected at normal speed, the reduction factor is 125. Thus a film taken in one second occupies the screen for more than two minutes.
As the incoming and outgoing film passes in contact with the same sprocket, the tension on the rolls is maintained, neither too tight nor too slack. The driving of the early motion-picture cameras was done by hand, and in some instances this method is still used. For amateur use (cinematography is not confined to the professional) clockwork mechanism is used in conjunction with 9.5 mm. or 16 mm. film. Professional camera work demands electric drive.
Electricity is the basis of the whole cinema industry. Cameras, the giant lights that are essential to the taking of moving pictures in the studio, developing, the printing of positive films from the negatives produced by the camera, projection, sound recording and reproduction — all are dependent on electricity. The modern camera can be equipped for driving from a battery, from the studio mains or from the remarkable diesel-driven portable power plants used in exterior film making. These power units are used primarily, however, not for the cameras but for the lights. They present a wonderfully impressive display of power, with high-speed diesel engines, mounted on huge lorries, roaring in concert with their humming dynamos.
The Vinten camera is an example of a modern high-speed camera. The film travels at 120 miles an hour and the spools are driven by an electric motor at 15,000 revolutions a minute. It is impossible to stop a film travelling at that speed, even for a split second, as in an ordinary motion-picture camera. The difficulty is overcome by dispensing with the claw mechanism and driving the film by sprockets continuously. The question of intermittence is settled by substituting for the ordinary single lens a ring of forty-eight perfectly matched lenses mounted in a large disk. The disk is revolved in front of the moving film at a slightly lower speed so that the exposure of one frame begins while that of the previous frame is still being completed.
The cinematograph projector may be described as the counterpart of the cinematograph camera: the mechanism is similar. Instead, however, of the light passing inwards through the lens to the sensitized film inside, light from an internal source passes outwards through a reversed film and a lens to the screen of the theatre.
Film developing and printing are carried out by ingenious automatic machinery. The light source in the modern film projector is so powerful that should the film stop for more than its appointed split second in the gate the celluloid inevitably catches fire. Celluloid is in itself an explosive and a film fire in the operating room is to be avoided at all costs. To guard against this risk the cinema engineers use another explosive as a safeguard. In close proximity to the gate of the projector a tube is placed, from which protrudes the end of a guncotton fuse. This fuse, unaffected by the lamp, leads back through the tube to a special valve that seals a high-pressure cylinder of carbonic acid gas.
Miniature Electric Furnace
Should the film in the gate catch fire the fuse instantly ignites and flashes back to the valve, which is immediately opened. The rush of inert gas then extinguishes the fire before any damage is done.
There is, however, a special slide behind the gate, and the operator is often able to snap this across between the film and the miniature electric furnace behind it. Furnace is not a misnomer for the source of light in the modern cinema projector, because the electric arc used yields the hottest type of flame known to science. The light emitted from the incandescent carbons, separated only by the intense flame of the arc, is immensely powerful — an absolute necessity in projection. The light must pass through a system of lenses, as well as through the film, and inevitably some intensity is lost in the process.
Further, the photographic details of every frame in the film are extremely small, yet they must appear greatly enlarged but as sharp and clear-cut as possible on a screen often a hundred feet away.
Two types of arc lamp have been devised for use in cinema projectors. In one type the incandescent carbon “crater” is turned directly towards the film gate. In the other type the crater is directed in a backward direction into a concave mirror that reflects the light forward again to the gate. For short-range projection, incandescent lamps are used extensively.
In a large cinema the great projectors stand in a battery, shut off from the auditorium by iron shutters which are raised as required to bring the machines into action when reloaded with fresh film.
Two recent inventions have revolutionized the film industry — the invention of the sound film and of the colour film.
FOR SLOW-MOTION PICTURES a camera of the continuous type is used. At the tremendous speed at which the film is run through the camera it is impossible to stop the film between exposures. The necessary interruptions are obtained by revolving, in front of the film, a ring of forty-eight perfectly matched lenses mounted in a large disk. Slow-motion cameras are used to solve many engineering problems.