"TALKIE" TECHNIQUE

Cue (NZERS), Issue 2, 30 June 1944, Page 3

" TALKIE" TECHNIQUE

HE acceptance of modern motion pictures as a universal 1 form of entertainment, as well as a means of education, has led many to overlook the rapid developments which have 'taken place in photographic processes from the early still pictures and lantern slides to the modern machine which brings a faithful reproduction of the camera and sound to the screen.

It is of interest, then, to glance back occasionally to the « Good old days » and review the early beginnings of ' many of our modern amenities. With motion picture developments, naturally, the picture theatre had its rise from the first still photos and, in tracing it’s progress, it is really essential initially to outline the principles which govern photography/ In the first instance it is necessary to have a negative, that is a carrier usually made of glass or celluloid, which supports a « light sensitive» agent in the form of salts of silver. In the camera this negative is held in a «light tight » compartment and the photograph is taken by exposing the film or negative to light passing through the lens of the camera. This process is brought about by the light being reflected from the object photographed and passing through the lens, impinging on the « light sensitive » material of the film and forming a latent image.

-As will be seen from the diagram, the image as reflected on to the negative, is reversed. This is due to refraction which causes the light passing through the lens to

cross. At this stage the picture on the negative is both upside down and opposite in tone value to the object. ‘ - In order to bring the image back to correct tone relationship with the object the negative is placed against’ a positive and light transmitted through the film.

This positive is merely another « light sensitive » material which is acted upon by the light passing through the negative. In this way with the reversal of position, light and shade tonings are restored to those originally in the subject photographed. /, . The time of exposure controls the amount of light to be admitted and also the extent to which the negative is acted on. Naturally bright light acts more or to a greater effect on the « light sensitive » material.

In passing to the next stage, it should be remembered that the action of the light on the negative is dormant until development, while « fixing » prevents further action by light. In other words, the « fixing » process makes the image immune from further reaction to light. . ■ ' The « fixing » process, further, is the stage where the developed « sensitive material » of the film is reduced to a metallic form, of varying densities. This metallic deposit makes up the picture or image.

An early stage in progress towards motion picture entertainment was the introduction of the lantern slide by which a powerful light was projected through a positive on to a screen, thus reproducing an enlarged replica as a still picture. The plates were hand changed. ~ This move was soon followed by the introduction of the silent picture which worked on the same principles as the lantern slide, with the exception that a roller film was used for flexibility and continuity. r The roller film ' principle was achieved in the taking of a series of pictures by exposing a part of the negative for a specified time, holding the negative still for exposure, and then quickly moving it on for a further exposure. Approximately the same speed is employed when the film is run through the projector. In this way a series of pictures, or frames, is obtained, each differing only slightly from the one before or the one after, while the film is devel- . oped and fixed in the ordinary way. The first success with a motion picture was achieved in 1895 by a Frenchman, Lumieres. For the reproduction of the moving picture on the screen, a powerful light is projected through a positive. Each frame (picture) in the series is held still in front of the light for a very short period — about 1/20 sec. for each—and then suddenly moved on thus bringing the next picture in front of the light. Thus on the screen is shown

a series of pictures, each differing slightly from the previous one, so that the illusion of a continuous movement is created. Undoubtedly the greatest advance made by the motion picture industry was in the period about eight years after the Great War when the «talkie,» after many years of research and disappointment, was introduced. The innovation was to them merely a linking of a gramophone record to synchronise with the visual picture and as can be quite realised and by some remembered, this method produced many difficulties. In the absence of single control, that is with the visual picture and the record, synchronisation was truly an art in itself, while it can also be appreciated that should the film- have required censoring, the process of eliminating the corresponding passage on the record presented many worries. In addition, a break in the film required an exact synchronisation on the resumption of the screening. PERFECT ANSWER. The modern « talkie » has eliminated all this and the introduction of the sound track has undoubtedly supplied the ' perfect answer. When the film is being made in the studio, a microphone turns the sound vibrations, that is the voice, music, effects, etc., into sympa-

thetic electrical current vibrations and these, passing through a neon type lamp—as shown in the dia-gram-give varying light intensities which in turn are projected on to the sound track space of the film. The sound track is ' usually on the right side of the . film looking from the projection box. When the film is developed and fixed, light and shade intensities, called the sound track, are produced. The reproduction of the : sound picture in a theatre requires a complicated and ingenious machine. Strong projection light is required for the visual film and, in addition, light is transmitted through the sound track. These varying intensities of light are impinged on a photo-electric cell, forward of the sound track, as in the diagram. This photo-electric cell comprises a type of valve with a light sensitive element which emits an electric current also varying in a direct ratio when exposed to varying intensities of light. The final stage is reached when these varying intensities of electric currents are amplified and transformed into sound waves by the speaker, concealed behind the screen reproducing for the audience an exact replica of the sounds and effects made in the studio.