The Cine Technician (1939)

June-July, 1937 THE flNE-TECHNI C I A N 47 The Visatone System of Sound Recordin; Capt. H. J. ROUND The following article is a report of a lecture given by Capt. H. J. Round, M.I.E.E., Director of Technical and Research Processes, Ltd., to The Association oj CineTechnicians, at The Crown Theatre, Wardour Street, on March \th. CAPTAIN ROUND opened his lecture by recalling that he was interested in sound recording as long ago as 1901, when he was still at the Central Technical College, South Kensington. Dudell, the inventor of the Oscillograph, was experimenting there at the time and he was fortunate enough to assist him in the making of these early recordings, which were of the type now known as Variable Area. The width of the track was rather wider than that in use to-day and the density was about -5, but this was probably the first recording done in the world, although some variable density work was being carried out by Rumer about the same time. He did not recollect that their recordings were ever played over and in fact no one was much interested, as the Boer War was then in progress. The subject was, however, revived again in 1929 by Captain Round, who produced a disc system which is now in extensive use. Disc recording was then the principal method used in England, and he thought it time to take up the question of sound on film. His assistant, Mr. Langridge, who is now at Stoll's, designed the first Sound Camera, and erected duplicating and fixing apparatus for rewinding film in 90 ft. lengths. This first recording was of one minute's duration and the only intelligible word was "the." Many difficulties were met with ; one of the greatest being to keep the speed of the film constant, although speed was a comparatively Evolution (continued from previous page) I have given the above description of this 1888 camera because if you read it carefully you will appreciate that it contains all the essentials to make cinematography commercially possible. It embodies the nucleus of all that appertains to cinematography even to-dav ; that is. a camera that carries a roll of material that is sensitive to light (the negative film) ; this film having imparted to it an intermittent motion so that it is stationary when the picture is being exposed, and when it is moved on for the next exposure, the light is cut off by means of a shutter ; resulting after development in a series of pictures (snapshots), one after another, on a long strip of material. William Friese-Greene succeeded in utilising celluloid film in the latter part of 1888. It is interesting to note, however, that when using paper before, he made it transparent by treating it with oil. It would be well for us all to remember that the Patent taken out in June, 1889, No. 10,131, by William FrieseGreene (copies of this document can be obtained from the Patent Office and a facsimile reproduction of the front page accompanies this article) constitutes the master Patent of the world for a camera that made cinematography, as we know it to-day, possible. This Patent has stood the test of time, having been upheld even in the American Supreme Court. With pride we should remember it was the invention of an Englishman. 7/ Oil-Coupled Fly Wheel. easy question in disc recording. It is now quite a feature of the Visatone system that this problem was solved in its infancy and no serious trouble has arisen since. Oil-damping was introduced in 1931 and is now in practically universal use. Another problem was mechanical oscillation, which could go on, once started, for as many as thirty or forty seconds, so Captain Round introduced a free fly-wheel inside the ordinary control fly-wheel with oil coupling and with such an arrangement oscillations died awav after about one-and-a-half oscillations. There seemed at one time some connection between flutter effect and sprockets, but no evidence was forthcoming to confirm this. If the recording drum was made to a certain diameter compared with the number of sprockets, the diameter being critical to a mil. or so, the film would be contacted by the first two sprockets alone, and no other sprockets would make contact. Furthermore, if the recording point was lour or five sprocket holes awav, any kick would lie filtered out. All the early work was done under the auspices of the Marconi Company, and after a demonstration to Sir Oswald Stoll, Visatone was fitted at the Stoll Studios, Cricklewood. The demonstration consisted of a three-minute film shol at 12 frames per second for the picture camera and 24 frames for the sound. Incidentally, the subject consisted of a game of cards between two typists and two clerks. At this point a change was made to area instead of density, and an oscillograph was constructed with a one-eighth inch reed and a minute mirror, and immediately