Kinematograph year book (1944)

Film Exhibition and Kinema Technique. 199 in light by the elimination of the shutter, which wastes 50 per cent, of the light from the arc. This is a point where many systems have failed, for while dispensing with a shutter they necessitate the use of smallaperture lenses, so nullifying any economy of light. An aspect of broader importance is the lessened strain on the film. The pull of the intermittent sprocket on the film amounts to about 6 lb., applied 24 times a second, imparting to the film an acceleration of over 1 mile per sec. The elimination of the intermittent motion would reduce these stresses to a mere fraction and overcome most of our troubles of emulsion pick-up and strained perforations. A recent British specification for a non-intermittent movement invented by Dr. O. K. Kolb, of British Acoustic, employs the, rocking mirror principle, but avoids the use of a shutter. Tests are being made in America on a chromium-plating method for worn projector parts. This, it is urged, will give longer life to the parts treated and help to solve the problem of the supply of new parts. The idea is a good one, but it must be recognised that chromium -plating of machine parts is not a new idea, the process having been employed for three or four years in some branches of engineering in this country. In precision engineering the measurement is so close that a new designing of the part would become necessary in many instances, as the three to five-thousandth-thick film of chromium would allow too little cleaiance. Where the surface has been worn down, the plating process would perhaps barely biing the surface to its oiiginal height. Plans for the post-war projection room and its equipment are already exercising exhibitors and technicians. More space is advocated for projectionroom suites, which should be a great deal more cheerful. Walls should be plastered and enamelled or tiled, floor coverings of light yet serviceable pattern, and the place should be as well air-conditioned as the auditorium . In detail, there is demanded a spacious rewind room, a rectifier room, a wellventilated battery room, and a combined workshop and storeroom, and R. Howard Cricks also wants a thyratron room for the house lights control. The future requirements of the kinema will require this greatly increased space, for, in addition to two or three 35-mro. projectors, there is the likelihood that a 16-mm. machine will also be installed. Then there is the slide projector, a couple of spots or, preferably, an effects machine ; nor must provision be omitted for the installation of equipment for a large screen television when it becomes a commercial practicability. Although there is little doubt that present-day national needs have stimulated and hastened research in the kinema industry as elsewhere, there is little immediate development to show, but a great deal of work has been going on behind the scenes and ideas and inventions primarily directed towards the war effort wilbbe applied to peace time entertainment, which will consequently benefit by the important advances made in design and performance of apparatus. One particular direction of progress is in respect to the perfection of the discharge lamp as a projector illuminant, thereby eliminating the heat, fumes and controls of the arc lamp. A great deal of work, however, is necessary before this will be more than experimentally available, although the various applications of the principle are being watched by the C.E.A. Technical Committee. It will be remembered that this method of illumination was employed in a dual projection outfit sponsored by Philips just before the war, containing two mute and soundheads, amplifier and all controls in the single unit. The suitability of new types of mercury discharge lamps, for various applications in photography and kinematography, is dealt with in a paper by H. K. Bourne, of B.T.-H., in the ''Photographic Journal." Three types of lamps are dealt with : the water-cooled capillary type, which is available in 500 and 1,000-watt sizes, has an exceedingly high efficiency, but needs a supply voltage of 600 and 1,200 v., respectively, and a supply of water for cooling ; the compact source type, made so far in 250 and 500-watt sizes,