International projectionist (Oct 1931-Sept 1933)

November 1931 INTERNATIONAL PROJECTIONIST 23 the light to each frame, that the upper outline of the hand and wrist belongs to one film image while the lower one belongs to the other. Above and below the thin hand and wrist, the faint outlines of the two original postures can be made out. Note also, that the index finger of the hand does not appear in the intermediate posture because it failed to overlap. The case in which light parts move upon a dark background may also be demonstrated. Irradiation The second phenomenon that enters into this art cannot be accounted for excepting upon the principle of irradiation.' A narrow fringe or border (either of light or shadow) , adjoining a larger area, will make the larger area appear to expand or move, with a variation in the illumination of the fringe. We often see examples of this phenomenon in advertising signs with raised letters that cast shadows. The variations in the illumination give an apparent motion to the letters. For similar reasons the thin arm of the colored boy will appear to expand upward or thicken to the limit of the upper outline of the fringe, if the' fringe be gradually darkened until it is the same shade as the rest of the arm. This apparent motion depends upon the variation of the illumination, and hence it is gradual and continuous and the equivalent of a succession of postures. It will be understood, of course, that these simulations of motion can occur only when there is an overlapping of the parts, and when the separation of the original postures is not too great. In watching this interesting phenomenon, and passing the film photographs through very slowly, it will be noticed that many of the couples give only a very crude representation of motion; but then again, others delight us with the grace and ease of the movements. Thus it is that this new art fills-in the dark-period with a real intermediate posture and a continuous succession of apparent ones. And in doing this, it performs a twofold service, for it eliminates flicker, and adds movement and life to the image. This unique property is the basis for a fair imitation of slow motion when the rate of projection is reduced to three or four frames a second. And in amateur cinematography it is invaluable, for it makes possible the taking and projecting of motion pictures at the surprisingly low rates of four to eight frames a second. The substantial saving thus effected represents the toll that flicker is now ex 'A ray of light; emission of heat rays; apparent enlargement of a bright object upon a dark ground. Showing two frames fully superimposed during the dissolve period. This tends to reduce graniness. The half-values of the highlights cannot be caught in a photograph, however: they show as white as the full values acting of the amateur. More than half of the cost for film goes out for apparently no better purpose than to speed up so as to make the flicker imperceptible to the eyes. Depth Possibilities V. Unusual third-dimensional effects, which are inherent in the dissolving or blending principle of the substitution. The two images superposed upon the screen at the same time are, undoubtedly, the chief reason for the noticeable roundness or plasticity of continuous projection. In Figure 2, the lap-dissolve is illustrated more strikingly by a frame of titles superposed upon a picture. If the film gate were here titled slightly with respect to the optical axis, the focal planes of the two images would separate, one of the images moving farther back of the other along the optical axis. It will be seen, therefore, that if the film photograph be moved downward from the upper position of the double aperture to the lower one, its image will occupy, successively, the more remote plane, the intervening planes, and then the nearer one ; and that at full projection speed, all of these planes will be filled with a sharply-defined image. This is another of the unique effects that can be obtained in this art, and which may be employed to accentuate the third-dimensional effect with an appropriate screen. Better Color Results VI. Better results in natural color projection, for the reason that the restrictions as to the rates of projection are removed, and methods giving better definition may be employed. In a recent article' the present writer " "Some Interesting Properties of Continuous Projectors," Journal, S.M.P.E. {June, 1931), Vol. XVI, No. 6. has summarized the mechanical advantages of the continuous cinematograph as follows: 1. A higher order of precision. 2. A more uniform and longer sustained accuracy. 3. The mechanism has fewer parts and is of the heavy duty type. 4. Oiling nuisance is avoided, and the sound track and picture surfaces are kept free from oil. 5. Noiseless operation. 6. Freedom from vibration, as all the moving parts are balanced and revolve at a uniform velocity. 7. Momentum of the prism-wheels tends to overcome certain inaccuracies in the mechanism. 8. Momentum of the film overcomes many inaccuracies in the perforations. 9. Wear on the perforations has less effect on the projection. 10. Momentum of film prevents sudden lateral movements. 11. Elimination of tension shoes possible, as a loose loop of film can be made to press itself with sufficient flatness against the aperture plate. 12. Elimination of tension shoes makes possible the use of raised or embossed margins on the film, thus forming an air-space and preventing scratches on the sound track and picture surfaces when wound up. 13. Absence of tension shoes eliminates the effects of variations in the thickness and smoothness of the film; and the effects of variations in the "give" or flexure of the film at the perforations when under a severe strain. 14. Minimum of strain and wear on film. 15. Fire hazard reduced as there is less possiblity of the splices parting. 16. Moving film fans itself, so withstands higher temperatures. 17. Even distribution of heat reduces buckling of frames. 18. Most of the work of pulling the film may be allotted to the frictional contact of the sprocket drum. 19. Minimum of work for the sprocket teeth prolongs their life. 20. Fewer and smaller perforations may be used. 21. The need of only one row of perforations, thus giving room for a wider sound track or a wider picture. 22. The use of one row of perforations eliminates errors in parallelism in the perforations and in the sprocket teeth, and makes for greater precision In the registration. Misleading Propaganda The advantages of the continuous cinematograph are, in fact, so many and so obvious that it is no wonder inventors throughout the world have directed their attention to its development. Several continuous cinematographs have been designed of such rugged and simple construction as to leave no doubt that they will stand up well under use. The charge that the continuous projector is impractical has been widely circulated in technical journals, to the prejudice of the art of continuous cinematography, and to the misleading of motion picture engineers. But obvious propaganda should deceive no one. And every one should know that the acid test for practicability is practice — the capacity for useful service. In its capacity for delivering uniformly accurate projection through a long period of time, the continuous projector stands out conspicuously among cinematographs. Its period of accurate use may be estimated at from five to fifty times as long as that of vibrating mechanisms. No greater claim to practicability can be made. [Note. — The second and ccmcluding article in this scries zvill appear in the next issue. — Ed.]