Kinematograph year book (1939)

280 The Kinemarograph Year Book. Elsewhere is reference to the projection lens introduced this year by Hummel Optical Co. The development in the high-pressure mercury vapour projection unit by Philips Lamp Co. may have a very significant bearing on the question of the projection illuminant. Meanwhile, however, the year has witnessed the continued popularisation of the A.C. high-intensity projection arc, the principal merit of which is the reduction of capital costs by the elimination of rectifying apparatus, although R. Howard Cricks, F.R.P.S., the " Kine. Weekly" expert, considers that properly run, the A.C. arcs show little difference in quality of light from that of a D.C. arc. A.C. arcs have been marketed by Strong, Brockliss, Cine Sales and G.-B. Equipments. As far as the D.C. arc is concerned Mr. Cricks considers the high-frequency H.I. mirror arc is firmly established. New models have been introduced by Zeiss | Walturdaw's), Ashcraft (Jack Roe), Kamm, and G.-B. Equipments. A new development of acoustic treatment is seen at the Warner Theatre, where Newall's Paxtiles are used to reduce the noise of the projectors and enable the projectionist to judge accurately the volume and quality of sound from the monitor loud-speaker. The work of the Guild of British Projectionists and Technicians continues to be invaluable to the trade : its members took a leading part in withstanding the situation caused by the abortive strike of the members of the E.T.U. and their efforts on behalf of technical education which has been extended, is not the least important part of its activities. A move urging that the Guild should affiliate to either the N.A.T. and K.E. or the E.T.U. was discussed early in the year but at its annual meeting it was decided to take no official steps in the controversy. Apart from the Guild's educational activities, various branches of the C.E.A. have sponsored courses at local technical institutions. These classes have been well attended and are proving valuable not only as a refresher course for employed junior but also in connection with the probationer scheme proposed by the N.A.T.. and K.E. PROJECTION ILLUMINATION SOURCES. Ashcraft Arcs. — One of the first experimenters in the field of the highefficiency Suprex type of arc was the Ashcraft Manufacturing Co., whose products are used exclusively by some of the leading American circuits, and for whose range of lamps Jack Roe is sole concessionnaire for this country. The range includes three types, two high-intensity and one low-intensity. The H.I. models, known as Types " D " and " E " are mechanically and optically of similar construction, embodying 14 in. elliptical mirrors and an automatic carbon feed which ensures a steady and consistent light over long periods without hand adjustment. Variation of feed ratio between the two carbons is provided by a cam and rocker system, giving infinitely variable adjustment over a wide range, and making provision for any future developments in carbon design. The carbon feeds are by means of chains, not screws, and back-lash is eliminated by means of powerful springs tensioning the chains. The difference between the two types is that the former has the larger lamp-house, and is better suited to higher currents, above 45 amperes ; although in practice it is found that only the largest of kinemas need to run at currents above 40 amperes, for which the Type " E " is quite suitable. Both lamp-houses are efficiently ventilated, and large dowsers protect the mirrors in striking. The L.I. model is substantiaUy similar to the larger types, except that the mechanism is considerably simplified. Carbon feed, for instance, is by a single chain, giving a one-to-one ratio, which does not, of course, need adjustment with low-intensity carbons. A 10|--in. mirror is used. The Ashcraft Co. promises Mr. Roe a new source of light in the near future, for which it is claimed that a pure white light will be shown on the screen at low-intensity cost. This new principle cannot yet be divulged pending the completion of patents, but should prove of great interest to every exhibitor.