International projectionist (Jan-Dec 1940)

Technical Data Anent Metal Film IN last article we confined ourselves largely to the development of metal film up to the year 1937. The article brought in such widespread and important inquiries that we have been able to form a definite opinion regarding the keen interest in metal film and its projection. The questions range from highly technical points regarding the reproduction of sound from metal film to practical points about speed of exposure, development and fixing of the image on metal. Tests in the laboratory of International News Service with positive emulsion gave printing times ranging from 1/10 second to % second in standard photographic printing eqquipment. Technical experts at I.N.S. were astonished at the speed of developing and fixing. By actual timing the entire printing process took exactly four minutes. We refer, of course, to a contact print in a standard printing frame. The four minutes was divided into one minute for loading the frame, x/2 second for exposure, 6 seconds in the developing bath, and the balance of the time was taken up in fixing, washing and drying with electrical drying unit. The developers used were standard metrol and hydro-quinone. In secondary tests we used amidol, and in fixing alcoholic solutions of hypo and alum. • Fine-Grain Metal Prints These printing tests took place in series over a period of three weeks. Critical examination of the metal strip indicated no chemical reaction has taken place to affect the metal or the printed image. It seemed a difficult matter to fog the emulsion even with a 60-watt Ruby lamp. All the operations in the darkroom were carried out under the same light that the laboratory uses for making bromide paper prints. The phenomenon that impressed the technicians in the photographic laboratory was the absense of grain in the emulsion on metal. The print finished in less than four minutes showed much less grain than the standard print on paper developed in fine grain developers, the latter printing taking more than 30 minutes. It becomes obvious that for metal the mind has to become oriented to appreciate this new medium in photography. We have developed negative and posi By Dr. ROBERT W. CARTER TAYLOR-SLOANE CORPORATION Tliis is the second and concluding article in the series which details the progress of metal film during the past few years. This installment discusses laboratory procedure, emulsion characteristics, splicing and editing, projection optics, and 16 mm. applications of this new motion picture medium. Acknowledgment for the privilege of reproducing these articles is made to George Blaisdell, editor of "American Cinematographer". tive emulsions that have a high gamma infinity, that are free from fog, even under the lighting conditions described, and have as high velocity content as cellulose emulsions. The advantage of such emulsions for motion picture negative will more than offset any difficulty that may be experienced in printing. Many of our correspondents were worried about editing negatives on metal. We have worked out a simple TABLE A Results of tests made by Electrical Testing Laboratories, of New York City, at the request of Dr. Robert W. Carter, are as follows: Material Submitted One front-surface silver mirror covered with a protecting coat of lacquer; one strip of metal ribbon 35 mm. wide ; one strip of exposed and developed 35 mm. film. Test The reflection factor of each sample was measured for an angle of incidence of less than 25°. Transmission measurements were made on the upper portion of one frame of film distinguished by the heading "Part I, Introduction". Results of Tests Trans Reflec Sample mission tion Factor Factor Front surface silver 0.94 Metal ribbon 0.89 Film 0.77 method for splicing that is not more troublesome than the method used for cementing cellulose film. When the negative is made and edited it will be permanent, fadeless and indestructible. The original metal negative will be preserved in the usual manner. Duplicates are made with standard optical printing by reflected light. • Reflection Tests To offset another misconception we print herewith the actual reflection tests (Table A). This test established the fact that the metal ribbon has a higher reflection factor and is more effective for optical printing than is printing by transmitted light through cellulose film. We believe that this should save the industry thousands of dollars on insurance rates and storage costs and fire hazard. We would like the many readers who are interested in microfilm, manuscripts, books, etc., to know that we will be able to put images on both sides of our metal film. This means that the reproduction of books such as the Encyclopaedia Britannica with its 25,000 pages, 8V2 by HV2 inches, weighing 126 pounds and occupying a cubic area of 4036 cubic inches can be microfilmed on metal to weigh 6 ounces and occupy a space of 10 cubic inches. To the many who inquired about the permanent reproduction of programs at radio stations we are pleased to report that this may be done very economically on narrow strips of metal film giving accurate tonal reproduction in the higher cycles. This record, of course, will be permanent, fadeless and economical. We have already constructed a simple reading machine for metal film. • Metal Film for 16 mm. We must apologize to the many readers interested in 16 mm. projection, inasmuch as we neglected to mention this important field. We already have emulsions developed for microfilm on metal that will give superior photographic images . with 16 mm. projection. We are confident that when production is commenced the price will not exceed cellulose film, with the added features of strength, permanence and positive non-inflammability. The technique for developing will give the same speed and the use of the film in the projection 10 INTERNATIONAL PROJECTIONIST