The Cine Technician (1939)

Aug. -Sept., 1937 THE CINE-TECHNICIAN 87 Lenticular Colour Films {continued from page 85). This is somewhat short of the required 5-8 times which is necessary to balance the filter loss. In addition to the above gains, the authors are of the opinion that the amount of screen illumination can be doubled if a sufficient improvement can be made in the operating conditions of the arc and the optical system. The product of this and all the above factors of gain gives 8-32 times, which leaves an ample margin for the projectionist in the operation of the projector when compared to the loss factor of 5-8 mentioned above. DEMONSTRATIONS The complete experimental projector was used to give two demonstrations in the Loew's Rochester Theatre in April. On both occasions the 52° accelerated pull-down was used. After the 68° pull-down was substituted, the machine was used to give a demonstration in the Centre Theatre in Radio City on July 9 for the benefit of some 200 invited guests. Many of these people commented on the show, but no one expressed any feeling that there was a lack of screen brightness. Some actually said they believed the screen brightness was higher than necessary. Although many measurements were made throughout all of these experiments of the screen illumination, a simple statement of the values in foot candles obtained would have little meaning in view of the conflicting reports already published both as to the screen brightness actually prevailing in theatres and as to the actual level of screen brightness that is to be desired. To give some indication, however, of the amount of light obtained on the screen in the Centre Theatre, the value measured with a Weston Illumination Meter, Model 603, without the colour filters or lenticular film, but with the shutter running, was 33 foot candles at the centre of the screen. The screen picture was 22 feet wide, and the projection angle was approximately 28°. If the heat absorbing glass filter were removed, the value would be more than 40 foot candles. FURTHER POSSIBILITIES Of course, every precaution was taken in both of these demonstrations to insure optimum operating conditions. It is probably too much to hope that optimum conditions could be thus maintained at all times. With this in mind, other possibilities will now be discussed with which still more light might be obtained. If the regular high intensity carbons were used, instead of the Suprex carbons, in connection with a reflection type lamp of most efficient design, there would be an increase due to the higher intrinsic brightness obtained with the regular high intensity carbons. The possibilities that a new type of arc source will be developed having a still higher intrinsic brightness cannot be excluded. In this connection, carbon manufacturers express the belief that development work now in progress will produce a carbon, which, with the proper optical system and lamp mechanism, will give the desired intensity, colour and uniformity of light, and at the same time, keep the energy input into the arc within reasonable limits. There are some improvements yet to be made in the present experimental optical system which will make it possible to eliminate some of the glass-air reflection losses. A desirable further improvement in the optical quality of commercial reflectors would reduce losses arising from the imperfect formation of the crater image at the film gate. The belief has already been expressed that improvement in projector design could be made which would further reduce the shutter loss. Another consideration is the possibility of a slight reduction in the screen size. Even for black-and-white projection, a reduction in screen size is being advocated by some in the industry. It is difficult to find any objection to doing this since, with the present sizes of screens, there is always a large block of seats near the front which the patrons avoid because of the discomforts of so large a viewing angle. There would seem to be no loss in desirable seating space by making conditions more comfortable for those in the front even at the expense of some loss in the rear of the house. Since the screen brightness would vary inversely as the square of the screen width, a considerable gain in illumination ought to be made possible by only a moderate reduction in screen size. The use of the ordinary specular screen would, of course, be limited to the long narrow houses where the seats are distributed within an angle of some 20. The design of equipment to take care of the few large houses with exceptionally large screens must be considered as a separate problem. CONCLUSION Although not all possibilities have been utilised in this preliminary investigation of the problem, it is seen from the foregoing experiments that lenticular colour films can be projected satisfactorily in the average theatre without the necessity of making major alterations in the present equipment. NEWMAN-SINCLAIR Price from £120 Send for Price Lift. AUTO KINE' CAMERA IS THE MOST MARVELLOUS CLOCKWORK DRIVEN CAMERA IN THE WORLD. It drives 200 feet Standard (35 mm.) Kine Film with one wind of the mechanism. It is reloaded in a few seconds. JAMES A. SINCLAIR & CO. LTD. 3 Whitehall, London, S.W.1