British Kinematography (1950)

March, 1950 91 TRENDS IN STUDIO LIGHTING EQUIPMENT Read to a joint meeting of the British Kinematograph Society and the Association of Cinema and Allied Technicians on 26th October, 1949 I. LIGHT CONTROL GEAR L. Hewins, M.B.K.S.* ARCS, the main source of light for colour photography, cannot be dimmed, and the only complete solution of the difficult problem of light control is, therefore, the provision of equipment which can regulate the light after it leaves the lens of the lamp. To achieve this result shutters of the Venetian blind type, hand operated, have been in use for a number of years, but during the last year, a motor, originally developed in America, has been made available in this country which enables the shutters to be operated, singly or in gangs, from a distance. This motor, known as the "Desyn" is designed to run off the same D.C. supply as the set lighting. Two types of controller are available, a hand controller, which will operate a maximum of 6 shutters, and a motor-driven controller which will operate 200 shutters in four gangs of 50 for lighting effects. The Desyn motor can be mounted on any shutter by means of one thumbscrew. Each motor is fitted with a reversing switch, thus enabling imperceptible changes to be made, from one light to another. Remote Switching This shutter system, which can quickly be fitted to almost any light on the set, fulfils the greater part. of the demand for light control, but remote switching is also needed on occasions. A variety of apparatus has been developed for this, including contactor units, for two 150-amp. circuits, contactor trucks for eight 150-amp. circuits, and hand-switch trucks. The Duarc strikes automatically, but other types do not. An automatic striker consisting of a solenoid which pulls the carbons apart against the action of a spring which can easily be fitted to an existing lamp by any maintenance shop, has now been made available. Mr. R. H. Cricks : May we know magnet, and the current is applied to the something about the synchronous motors field coils from the controller. When employed ? the controller is turned, it energises the fields The Author : They are similar in opera in rotation, and the armature follows the tion to A.C. Selsyns, but they are designed magnetic field around the poles, for operation on D.C. They are silent in Mr. F. G. Gunn : When the lamp is operation, smooth in action, and capable shuttered for a comparatively long period, of being revolved at speeds up to 300 r.p.m. does it give rise to considerable temperature A Visitor : Are they synchronous revolu rise ? tion for revolution ? The Author : It is not desirable to leave The Author : Yes, when they are con the shutter closed for too long. But for nected to the same controller. The pole normal set working it is safe to leave the pieces are skewed in order to obtain the shutter closed for five minutes or so. smooth action ; the rotor is a permanent II. CARBON ARCS C. G. Heys Hallett, M.A., M.B.K.S.* TWO studio arc lamps have been selected to illustrate the trend in British design. One of them, the Type 1450 or more familiarly " The Brute," is already well-known,1 though it has only become available within the last 12 months, but the other, " The Junior Brute," is announced to-night for the first time. " The Brute," which at a current of 225 amps, or 50 per cent, more than the * Mole-Richardson (England) Ltd.