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The introduction of the sound film brought about a revolution in the cinema industry, which, although comparatively new, has been developed continuously by the invention of new processes. A later development, the colour film, is now a commercial success


IN THE PROJECTION BOX of the Mayfair Cinema, Liverpool

IN THE PROJECTION BOX of the Mayfair Cinema, Liverpool, where the “ Mirrophonic ” system of sound reproduction is used. Sound is reproduced from a sound track incorporated on the film itself. When the reel in one projector is finished, the second projector comes immediately into operation. A special changeover switching device ensures the continuity of synchronous sound reproduction.

The coming of the cinematograph, described in the previous chapter, caused a revolution in the entertainment world comparable only with the introduction of radio broadcasting. The industry that gave silent films to the public for more than a quarter of a century was destined, however, to undergo a revolution within itself. Pictures were to advance far beyond the stage of movement alone. Speaking, singing, music, the splash of water, the roaring of fire, the noise of motor cars or machine guns — all have now become commonplace to the cinema audience.

The silent film, however, is still used for engineering purposes. Sound is often matched in with silent films, especially those of an educational nature; news reels and cartoons (prepared from thousands of drawings) are also provided with commentary or music after the photographing. Before its eclipse as the standard form of entertainment, the silent film had reached a high degree of perfection. The subtitles of the silent days were a necessary evil, although in most cinemas there were plenty of people willing to read the words aloud for the common good. Sympathetic music, often from a good orchestra, was a well-known feature of all film shows.

All that, however, has now been changed, and with it the whole technique of motion picture production and presentation. A striking instance of this change is provided by the. studios in which pictures are made. For the silent film the studio was a babel of noise. Now that sound is of vital importance the greatest asset of the studio is silence. Cameras, lights, movements of players —all are silenced with scrupulous care for the benefit of the microphones that record speech and music. The wonderful recording systems now in use were not perfected without the most painstaking experiments extending over many years. Edison was one of the first men to associate the cinematograph with the recording and reproduction of sound. In later years many attempts were made to synchronize Edison’s gramophone with the cinematograph, but the results were not entirely successful.

In modern cinemas the synchronized sound that accompanies the talking picture is derived from the film itself and it is stored there by the same means as the picture — by the use of light.

The first man to demonstrate the use of light for the transmission of sound was Edison’s contemporary, Alexander Graham Bell, inventor of the telephone. Bell’s “photophone” of 1880 is referred to in the chapter “Evolution of the Photo-Cell”. This device was, developed further by a German scientist, Herr Ruhmer, who succeeded in talking along the beam of a searchlight, for a distance of several miles. Ruhmer also recorded, on a strip of film, light variations caused by sound waves.

This brilliant idea of Ruhmer’s and the cinematograph as developed by Friese-Greene in England were both studied by another clever inventor, Eugene Lauste, whose original British patents covered the photography of sound waves on the cinematograph film. Unfortunately, Lauste’s patents were allowed to lapse, but the evolution of the talking film during and after the war of 1914-18 was in no small measure due to his genius.

Lauste was able to reproduce the sounds recorded on his film, by the use of a selenium cell, but the difficulty was to amplify the reproduction for the benefit of an audience. All kinds of devices were tried by various people to amplify the faint sounds of the light-sensitive cells used for the first experimental talkies. It was not until the introduction of the amplifier valve by the scientist Lee De Forest that the problem of audibility was solved. Many other branches of science received an enormous impetus at the same time.

Although the early attempts to synchronize the cinematograph with the gramophone were not successful in this connexion, the pioneer work of Hepworth is of special interest. Hepworth also invented the automatic film-developing method used throughout the world. In Hepworth’s “Vivaphone” system the artist sang or recited before a camera and a gramophone recording instrument.

First Successful Sound Films

In reproduction the gramophone record was played in front of the screen and the instrument was linked with the operating room by an ingenious electrical signalling device. Despite risks due to the “human element” in starting the gramophone at the correct moment, rights in the invention were acquired by the Western Electric Company of America. Under the name of “Vitaphone” the system was used for the first commercially successful talking films, The Singing Fool and The Jazz Singer. In these productions each reel of film was synchronized with a 16-in. gramophone record.

The modern film, however, is dependent for its sound on itself. A narrow strip at one side, close to the perforations, provides the “sound track”, as it is called. Recording on the sound track may be done by two different methods, both being referred to in Lauste’s patent specification. They are known respectively as the “variable density” method and the “variable area” method.

In the“variable density” method the sound variations picked up by the microphones are photographed on to the sound track by a lamp, the light from which can be varied in intensity. This variation of the light is accomplished by masking, with a loop of wire, a narrow slit through which the beam passes to the film. The loop of wire is placed between electro-magnets, and as the electrical impulses from the microphones pass through the wire the sides of the loop open and close, but only by a microscopic amount.

The amount of liPRINCIPLE OF THREE-COLOUR CINEMA PHOTOGRAPHYght passing through the loop and slit is thus varied in intensity by the action of sound on the microphones. The beam of light that impinges on the sound track of the film is necessarily extremely small. It would be difficult to maintain a slit only a thousandth part of an inch wide free from dirt, so the light slit is made fairly big and the resulting wide beam is reduced by an arrangement of lenses, so that when the beam impinges on the film it is the correct size. The variable density sound track appears as a series of horizontal lines which range through various tints from light grey to dark grey.


Key to Diagram. A—Lens. B—Optical device which divides light from the lens between two apertures (C 1 and C2) at right angles to each other. D—Green filter which transmits green light only. E—Panchromatic film receiving green image. F—Magenta filter which transmits red and blue light. G—two films with emulsion surfaces in contact. The front film absorbs the blue light, and the rear panchromatic film receives the red image.

The “variable area” method of sound recording uses a loop and electro-magnets somewhat similar to the above, but the wires do not open and close with the current fluctuations from the microphones. Instead, the loop, which is fitted with a minute mirror, turns slightly between the magnets in accordance with its electrical impulses. The light from the lamp is focused on to the mirror and the reflected beam is directed to and fro across a slit giving access to the film. The variable area sound track thus appears as a zigzag margin with clear film on one side and exposed film on the other. Sound recorders of this type, are capable of dealing with vibrations of all frequencies from twenty-five to 15,000 a second.

The various components of the sound-recording equipment are housed in a “sound-head” attached to the camera. An important feature of the sound-head is the arrangement of the film. As described in the previous chapter, the film passes through the gate of the camera in a series of jerks. These jerks, of vital necessity for the picture portion of the film, would be fatal to the successful recording of sound. Accordingly the film, having left the camera gate, is slackened slightly so that it passes the light slit at a steady uninterrupted speed. The film records first the scene before the camera at about twenty-four pictures, or “frames”, a minute, and then passes to the sound-head for the recording of sound.

This method of recording pictures and sound simultaneously on the one film is not used, however, for general work in the cinema studio. It is used in the making of news reels and similar films. Studio sound recording demands absolute silence, and extraordinary precautions are taken to ensure that no extraneous noises shall reach the microphones and so spoil the film.

It is not generally known, perhaps, that two films are used for every shot or scene, one for taking the pictures, the other for recording the sound. The pictures are taken by a camera in the studio, and on this film a blank space is left for the sound track. The sound-recording apparatus, using another film, is located at some distance from the set and is firmly bolted down and insulated against vibration. This film records only the narrow sound track, leaving the picture portion blank.

Matching Pictures and Sound

The electric motors that drive the picture camera and the sound recorder respectively are synchronized so that the two films run in step. When the two films have been developed the picture film negative is printed by a lamp on to a positive film (ready for the projector) with the sound track space masked. The mask is then dispensed with, and the sound track of the positive is printed from the sound film negative. It is essential for the pictures and sound to be in step during the printing process or the careful synchronization of camera and sound-recorder goes for nothing in making the film. To ensure that the two films shall be correctly matched when superimposed in the printing machine the technicians use what are generally known as “clappers”.

This ingenious yet simple device consists of two boards that are brought together with a loud clap in front of the studio camera before a “take”. The camera, which is turning, takes a motion picture of the boards as they meet, and the noise of the clap shows up on the sound track as a black line. When printing it is necessary only to place the picture of the boards in the closed position on top of that portion of the sound track displaying the initial starting black line.

The printing machine consists of a framework that holds on one side the full spools of developed negative film and undeveloped positive; on the other side are the empty spools to which the two films pass. In the centre of the machine is a brilliant electric light over which the films, held in close contact, are drawn by sprockets driven electrically. In addition to machines for the independent printing of pictures and sound track, there are machines capable of printing pictures and sound on to the positive in one operation. Any number of positives can be printed from the negative film.


FILM PRINTING MACHINE which prints pictures and sound track on to the positive film in one operation. Developed negative and undeveloped positive are passed, in close contact, across a brilliant electric light. Any number of positives can be printed from one negative film.

Developing is different from the “agitation in a dish” of ordinary darkroom procedure, although the two processes are chemically similar. The modern developing machine permits the continuous treatment of film hundreds of feet long. In one type of automatic developing machine the film is fed into a tank of solution by an electrically driven sprocket, whose speed can be varied to control the degree of development. The film is passed several times through the developing solution and is then drawn through tanks of water for rinsing. Next follows the fixing process, and finally the drying in a chamber where the air is automatically conditioned.

Another interesting automatic developer has, instead of tanks, numbers of ebonite tubes about twenty feet deep. The tubes are placed in rows, and over every row is a shaft carrying a number of sprockets. Every tube has its corresponding sprocket, whose speed is adjusted by a small clutch. The film is inspected after its journey down and up the first tube and the degree of development is adjusted in subsequent tubes by the length of the loop that is allowed to dip into the solution. Generally the first three tubes contain developer, the fourth rinsing water. The fifth and sixth tubes do the fixing with hypo solution, and then comes a number of washing tubes. Finally the film is dried by a vacuum device and passed to the winding spools. When it is desired to tint the films, additional tubes, containing dye, are used. The utmost care is required in developing to avoid stains on the sound track as these would spoil reproduction.

With the sound recorders, printers, developers and other highly ingenious machines playing an unobtrusive yet essential part behind the scenes the studio still takes pride of place as the show piece in film production.

Magnified Models

Apart from cameras, lights and microphones, any number of ingenious gadgets and photographic tricks are used in the studio. The noise effects are produced by the same methods as are used in radio broadcasting. The sound of a few matches rattled in a matchbox in front of the microphone is heard by the audience as the gentle lapping of water against the side of a boat. Sound engineers gently roll some small shot on the parchment head of a drum and the audience hears the sound of waves on the shore.

Exact scale models also serve in the studio and help to cut down the enormous expense of building full-size sets. One ingenious method is to reflect a scale model, say, of the upper stories of a street of houses, in a mirror that faces the camera. The back of the mirror that reflects the framework below the model is then scraped away and the camera looks through the glass to a full-sized set representing the lower stories of the street. The cast can then act in front of the set and the camera records the acting with a complete set of houses.

CINEMA CAMERA of the Vinten Model H typeMany highly important developments have been introduced to cope with the necessity for silence in the studio during the making of a talking film. The modern film studio now resembles that used for radio broadcasting, with its insulated walls and red warning lights.

CINEMA CAMERA of the Vinten Model “H” type, the magazines of which hold 1,000 feet of film. The camera, mounted on a special tripod, is driven by a 230-volts single-phase electric motor. For studio work the camera is covered by a hood or “blimp” to deaden all sound.

Silent-film cameras were formerly noisy, but camera engineers have now succeeded in producing an instrument that is almost silent in its action. To make sure that no faint whirr shall reach the microphones, however, the camera is covered by a special box known as a “blimp”.

The studio microphones are held in stands, on long arms, or booms, stretching out from special portable cranes, or they are suspended from overhead wires. Care has to be taken to avoid the casting of shadows by these instruments on the set. Impulses from the microphones do not go direct to the recording apparatus. The electric cables are first led to a “monitoring” cabin with a glass front. In the cabin is seated an operator provided with headphones or a loudspeaker. It is his duty to watch the acting and control the “mixing” of the various microphones so that the sound record shall be as nearly perfect as possible.

Another technical aspect of studio work that demands special attention is the lighting. In the days of the silent film the essentially brilliant lighting of the studios was done by powerful arc lights, but the hissing and spluttering of these lamps made it impracticable to use them within range of the. microphones. The arc lights were replaced by large incandescent lamps, that rapidly grew in size and power. This change provides an interesting example of the way in which one invention is dependent on another in technical development. The incandescent lamps give a light that contains a large percentage of red rays — virtually useless for ordinary film exposure. Modern films, however, are panchromatic, that is to say, they are sensitive to red rays which on ordinary film photograph black.

The giant studio lamps are rated at over 11,000 watts and their filaments, as thick as lead pencils, are supplied with electric current which produces extremely high temperatures. The stands that carry these giant lamps run on wheels provided with compressed-air brakes to ensure smooth stopping on the set; this ensures a longer life to the expensive filaments. Special starting devices are used to feed the current gradually to the studio lamps: otherwise they would blow up. The lamps are cooled by electrically driven fans. Sometimes outside recording of important events is carried out on similar lines to studio work. News-reel vans are now a familiar sight at most big public functions. A modem new -reel van contains a motor-driven generating set that supplies current for the operation of the equipment, an amplifier and monitoring loudspeaker and control gear. In the van also is a sound recording “camera”.

THE SOUND-FILM PROJECTORLeading out from the back of the van are numerous rubber-covered cables, each 100 yards long, that are connected to a “mixer”, from which lead other long cables carried in drums on a trolley. These secondary cables lead out to the microphones. In the recording van an operator sits at a desk and notes the volume and quality of the sound passing to the recording camera. Another operator is stationed by the mixer and his job is to control the operation of the microphones. He is provided with a pair of headphones for monitoring purposes, and also has a telephone for communicating with the operator in the van. The cameras are driven by motors which are synchronized with the motor of the recording camera.

THE SOUND-FILM PROJECTOR is in some ways the counterpart of the camera. Above the lower reel of this projector is the sound-head, in which an intense beam of light is focused on the sound track of the film. A photoelectric cell transfers the variations in area or intensity of light to the sound reproduction apparatus.

The projector used for the reproduction of sound films may be regarded in some ways as the counterpart of the camera. The brilliant light of the projector shines through the film in the gate and a system of lenses, through an iron shuttered opening in the operating room wall and so to the screen at the distant end of the cinema. Below the projecting apparatus is another projector in miniature, the sound-head, in which a small but intensely brilliant light is focused on to the sound track. The light shines through the sound track on to a photoelectric cell. The cell thus enjoys a film performance of its own, comprising a mixture of light and shade or zigzag lines according to the system used.

Below the camera gate (where the film moves in jerks) a loop is left in the film to enable the strip to pass smoothly through the sound-recording device. A similar loop is used in the projector. In the “Mirrophonic” system (variable density) the film in the sound-head passes round a “kinetic scanner” or drum, provided with a flywheel and clutch that ensures absolutely smooth running. Inside the drum, which is pierced for the light beam, is a prism that turns the ray at right angles on to a photoelectric cell at the side of the scanner. All the projector gear is electrically driven.

The most recent development of the film industry is an intensified search for a method of portraying scenes in natural colours. Numbers of different systems have been evolved and among them one of the most interesting is the “Technicolor” process. The technical problems that have faced those working on the process have been enormous, but it has now become a commercial possibility.

Filtered Colours

All colours can be matched by a mixture in the correct proportions of three primaries, now said to be red, blue and green. It is this general three-colour principle that is used in the ‘‘Technicolor” process. Three films are used. One film receives, through a filter, only the green in the scene before the lens. Between the lens and the green filter is an ingenious optical device that divides the incoming light and turns part of it at right angles through a magenta filter, which transmits blue light and red light. Behind the magenta filter are two superimposed films, emulsion sides touching, one sensitive to blue and the other to red light. The three films are run through the camera in the usual way and are then developed separately. The three resultant negatives are separately printed (by light) on to specially prepared films. These are also developed and treated to yield positive images in relief of hardened gelatine. These gelatine matrices may be regarded as long continuous blocks such as are used for printing magazines. The three hardened gelatine film blocks are then used in an interesting three-colour printing operation that can be repeated at will to make any number of positive films for distribution and projection.

The matrices are treated with their appropriate colour of dye and are pressed, in turn, against the prepared blank film. This printing operation is continuous and great care is taken to ensure the correct registration of the three matrices relative to the positive film.

There is a universal appeal in the coloured film, reminiscent of the coloured slides of a magic lantern, yet brought to unbelievable perfection.

INTERIOR OF A MOBILE RECORDING UNIT as used for production of news reels

INTERIOR OF A MOBILE RECORDING UNIT as used for production of news reels or films “on location”. A complete sound-recording unit is installed in the van. On the right is the motor control panel and on the left is the recording main amplifier. Above the camera are the recording lamp and oscillograph control unit and the monitoring amplifier.

You can read more on “Evolution of the Photo-Cell”, “Story of the Cinematograph - 1” and “The Triumph of Television” on this website.

Story of the Cinematograph (2)