The motion picture projectionist (Nov 1929-Oct 1930)

40 The Motion Picture Projectionist January, 1 930 Tor the WzVjzeH^Projection of Notion Pictures " Actodector can be counted upon to do its part. Its intense, constant, and dependable flow of power is absolutely unrivaled. It is a Motor Generator Set especially designed to meet the particular conditions in the projection booth. Would you like full information? Write — ROTH BROTHERS & CO. Division of Century Electric Co., St. Louis, Mo. 1400 W. Adams St. CHICAGO, ILL. Distributors in all principal cities of the world New York Office: Century Electric Co., 50 Church Street IN WESTERN CANADA! CANADIAN THEATRE SUPPLY CO. Authorized distributors for SIMPLEX— MOTIOGRAPH— POWERS— HOLMES and all theatre equipment of the leading manufacturers. Also, an extensive line of stage equipment. Complete Sound Picture Service! 105 Capitol Theatre Building Winnipeg, Man., Canada Alberta Representative M. L. ADAMSON 1605 — 104th St., Edmonton, Alb., Canada Color Cinematography (Continued from page 31) matography will enhance the impression of relief and of distance. The manner in which bi-chromatic cinematography has been applied to medicine by means of the clever Busch apparatus proves that, notwithstanding the incompleteness of the sensation, the effect obtained is much more demonstrative than anything that can be obtained by ordinary cinematography, and the greater truthfulness of the picture certainly produces the effect of making the details stand out with greater relief. Positive Film and Printing A film of celluloid coated with a double stratum of sensitive emulsion, one on either side, is unquestionably the kind best suited to bi-chromatc cinematography. The usual emulsion employed for cinematographic positive films intended for ordinary projection is used. But two circumstances must be allowed for in printing the positives, one of a mechanical and the other of a physical nature. The printing machine must allow a single series of images to be printed on each side of the film ; hence it follows that the two films — the negative and the rough positive — cannot be printed in the ordinary way, it being necessary to jump one image: — only by this means is it possible to print one one side a continuous series of images intended to supply the monochrome red and on the other the monochrome green series. This does not involve any very arduous mechanical problem, but it is obviously necessary to have a printing machine which allows the negative films to be moved at just double the speed of the rough films. Fixing Process This latter difficulty is completely eliminated by dyeing the emulsion yellow; thus for instance a slight degree of coloring with tartrazine yellow removes the difficulty without affecting the print, while the yellow coloring disappears entirely in the course of developing, fixing and washing the film. Or again a stratum of hydrate of bi-oxide of brcwn manganese, precipitated in the emulsion, renders the stratum quite opaque, while the manganese composition can very easily be removed by using a solution of hyposulphite containing a sufficient quantity of bi-sulphite of sodium for fixing. The development of double-faced films calls also for some special arrangements which are quite easily made. By recourse to the methods above indicated, we obtain a positive film bearing a double series of black images, one on either surface ; each of these series of images must afterwards be converted into the corresponding monochromes.