British Kinematography (1950)

84 Vol. 17, No. 3 ELECTRICAL DEVICES AS APPLIED TO SPECIAL EFFECTS Presented to a joint meeting of the British Kinematograph Society and the Association of Cinematograph and Ailied Technicians, on March 29, 1950. I — PROBLEMS OF REMOTE CONTROL John Gow* THE Special Effects department at Pinewood Studios has in the past consisted of four sections : the matte, miniature, process projection and stage effects departments, and each of these departments calls for electrical devices. In the main, problems involve the motorisation of a moving unit, such as small models, revolving globes, moving glasses. In stage effects, the opportunities give more scope to ingenuity, and permanent pieces of equipment have been evolved, each utilising electrical power of some kind or another, such as fog generators, rain machines and weapons of all kinds. Control of Process Projectors. In the field of process projection, we have utilised electrical power, other than the normal direct current which supplies the arc, to assist production. During the last few years, projectors have changed quite appreciably, and we now see a complex use of small electrical units incorporated to assist in speeding up production and to produce effects hitherto only dreamed about. As arc lamps have increased in light output, heat has also increased, and it has become necessary to remove some of this heat in order to keep the film or slide in a reasonable condition, and to safeguard the glass lenses incorporated. This has been achieved by the introduction of an ON 20 glass which absorbs some of the unwanted heat, and removing this heat by circulating cold water over its surface ; the water also cools the No. 1 condenser at the same time. The water is kept circulating by the use of a pump driven by an electric motor.1 At the output end of the projector we have the lens, and this has been mounted in a cradle which will move in three directions, each of these movements electrically controlled, and from a remote distance. To achieve this, Selsyn motors have been used, and from a master motor at the camera position, a slave motor attached to the lens mount is made to operate. The principle was used during the war for controlling guns from a remote distance. We now can, from the camera position, obtain focus, rise and fall of pictures on the screen and also horizontal movements.2 In the still process projector, accuracy of registration is often necessary between background and the foreground set. On the latest equipment, no fewer than six movements are controlled by means of Selsyn or Magslip motors from the camera position : focus, vertical and lateral centring of the picture, and vertical, horizontal and circular movement of the picture. The size of slide has been increased to 5 ins. x 4 ins., permitting it to be traversed for effects such as clouds.3 Recording Camera Movement. These small and efficient motor units can be, and are being, used for other purposes of remote control, and can be utilised for remote camera focus or camera movement when necessary.4 We are at the moment developing a slave head for use with the travelling matte process, the idea being that any movement of camera on the foreground action is recorded and the movement duplicated when shooting the background, * J. Arthur Rank Productions, Ltd.