The Cine Technician (1953-1956)

March-April, 1952 THE CINE -TECHNICIAN 45 studio goes all magnetic, it is possible that the disadvantages may be transformed into a positive advance in the technique of sound editing. In England at present, magnetic film has been used largely as an additional facility rather than as a direct substitute for photographic methods. Films have been made with all exteriors and location work done on magnetic with a considerable economy, but in most cases the magnetic record has been transferred to photographic in the studio. At Gaumont-British Instructional, using the Gaumont-Kelle system, more use has been made of magnetic recording than in most studios. G.B.I, is primarily a documentary Company but it uses normally more than 30,000 metres of film stock for sound yearly, producing 150 reels of finished film. The use of magnetic recording is hoped to produce a great saving in the cost of this film and its processing. The Sound Chief of G.B.I. reports that they use magnetic for commentaries, music, post-synchronisation of voices and effects, and premixing. Extra time is required for the transfer of suitable " takes " to photographic, and needs a staff of three, but it is easily possible to transfer suitable materials from 8 reels (2,400 metres) in three hours' work. For ease of working it was found essential to have a centralised department layout, with magnetic and photographic channels and darkroom adjacent. There has been little opportunity during production for testing and adjusting the equipment but it is robust and there have been few technical modifications necessary. The equipment is tested weekly and apart from a slight wear on the faces of the heads the setting has required little alteration. " Ghosting," caused by strong images setting up magnetic shadows fore and aft, seems to be a function of the material coating of the stock. It is not serious at its worst and most stock is free of it. There has been no distortion due to speed variation. Imperfect wiping can usually be cured by resetting up, but it may be a potential trouble. In general the reports on the quality of the sound are excellent, the absence of background noise is particularly noticeable. There has not been much investigation into the problems of editing, but with regard to the possible variations in the sensitivity of stock and the fact that joins, although not always noticeable, may require a special blooping technique, it is considered advisable to use complete rolls of material when possible. In America there have been more developments in the use of magnetic recording. In particular the methods that have been developed by Paramount Pictures are of some interest. A considerable number of productions have been made by them in this way, and all future ones will be. For production recording a lightweight magnetic channel with a two-way mixer is used, weighing in all about 50 kgms. Two recorders are used to avoid delays in reloading and to give instant change-over in case of trouble. The recorder is turned over simultaneously with the picture camera. Synchronisation is automatic, without clappers. At the end of the day's work, the takes to be printed are transferred to direct positive photographic prints by a supersonic variable density method. This is a method of variable density using toe recording. A supersonic bias — 24 kc/s — is superimposed on the light valve ribbons to convert the light transmitted by the valve to a wave shape, which, when combined with the toe record, gives a linear relation transmission. Direct positive prints may also be made with variable area (SPME Journal, Vol. 33, Nov. 1939) using a noise reduction envelope recorded in advance of the signal. A fine grain high contrast emulsion is used with a density of 1.0 to 1.2. The transfer reproducer is equipped with a counter and is capable of fast winding both forwards and backwards. The operator fast winds down through the roll of film until he hears the synchronising click for the first take. The transfer is then made electrically to the direct positive print. The direct positive recording machine is equipped with a special photographic marking device that exposes production number, scene number and footage, at one foot intervals along the edge of the film. For music recording double recording channels are used alternately, and when a good take is obtained, the film is ready to go to the re-recording channel without further processing. All rehearsals are recorded, so in fact the first good rehearsal is the printed take. Editing is simplified by the use of special transferring machines, magnetic to magnetic. This transfer is used in place of cutting and splicing, and so all the difficulties inherent in the use of joined magnetic film are avoided. Tracks are laid for re-recording purposes on continuous lengths of magnetic film, all sound effects being laid magnetically in their correct position. Magnetic dialogue is transferred in the same way to continuous rolls of film. All synchronisation is by edge numbers. All re-recording is by magnetic film, and the sound is then transferred to the release photographic negatives, which is the only photographic negative used in the entire process. The magnetic film need not be cut or marked so it can be used many times without difficulty. With regard to the equipment used for magnetic recording, the requirements of synchronisation and the need for constant speed and freedom from flutter are the same whether magnetic or photographic means are used. Magnetic equipment for studio use has been designed, in most cases, on the same lines as photographic, and in some cases is interchangeable for the use of both methods. It is often the practice not to include an erasing head in the production sound camera, because it is found preferable to use a centralised erasing procedure to prevent accidental loss of recorded material. 35 mm. coated film of 17 1/2 mm. or split 35 mm. film is usually used with this type of equipment, the sprocket hole type of carrier being used to maintain constant speed. Although magnetic recording for synchronous purposes has been adapted to existing recording standards, there are several advantages claimed for the use of narrow imperforated tape. It is considerably lighter and occupies less space as well as being much cheaper. The frequency response characteristic of tape is better than with film although this is not so important when the response of existing reproducing equipment is considered. The improvement in response and also quality, is due to several reasons. Among them is the greater flexibility and better head contact of tape, and also the better uniformity of the coating. Coating of film base is still rather a variable factor but much work is being done to improve it. Tape has the disadvantage of having a variable slip that makes good synchronising difficult although at the same time the danger of sprocket hole flutter is elimininated. It is possible to obtain synchronisation by means of pulse recorded at the time of the original recording. The playback speed is governed by the pulse frequency. The greatest disadvantage of tape, Turn to pnye iU