American cinematographer. (1939)

METAL FILM STEADILY 3U2 Madison Avenue, New York THE advent of metal film for prac¬ tical use took place in November, 1938. Previous articles in this magazine have detailed the history and technical development of metal film since the first decade of this century. Executives, exhibitors and experts in the motion picture field have witnessed demonstrations of pictures and sound from metal film. They were unanimous in their opinion that metal film has an immediate and widespread use in the entire projection field. The writer is grateful for the flood of inquiries which followed the appearance of the previous articles and takes this opportunity to discuss and answer some of the principal problems and queries presented in the correspondence. It should be stated at the outset that metal film will in no wise jeopardize the present status of the professional motion picture operators. It is true that the fire hazard has been completely elimi¬ nated. It is also an established fact that metal film will not break or tear in its passage through the projection machine. Concentrate in Projection We submit that with the removal of these hazards the operator will be better able to concentrate his attention on his main objective, the superior projection of motion pictures. The first machine used for the pro¬ jection of metal film was an adaptation of a standard model with gate, optical system and soundhead converted espe¬ cially for this purpose. The machine was so constructed that it could serve a double purpose. It could be used for the projection of both standard cellulose film and metal film. The task of changing from one to the other was a matter of a few seconds. For metal, the lamp is swung to the front, a special gate is put into posi¬ tion and the metal film is threaded through the other soundhead which is specially constructed for metal film. This first machine gave us the basis for a fair comparison between metal and celluloid film, since both could be pro¬ jected from the same machine under the same conditions. The tests proved that metal film was equal to celluloid film in pictorial quality and slightly superior to celluloid film in sound value. Physical Facts For the benefit of those who desire the fundamental physical facts about metal film we state the following: The film is constructed of a special alloy and is usually .003 inch in thickness; the image is on a highly reflective surface, and projection is by reflection from this surface. A reel of 1000 feet, 35 mm., weighs 6V2 pounds. The film may be spliced with a special cement in the usual man¬ ner. The film is threaded through the projection machine in the standard man¬ ner with the exception of one sprocket which leads to the reflecting soundhead. The film is not affected by the heat from the lamp. It will never shrink or stretch, and with ordinary care will last indefinitely. The optical system does not require condensers or any device to prevent the light ray from striking directly upon the film. The full power of the light is impinged directly upon the metal film as it passes through the gate aperture. The light reflects directly from the polished film surface through the lens to the screen. Information regarding the optical system is found in the American Cinematographer for September, 1938. This article also gives a reproduction of the actual tests of the reflection factor of metal film as compared with ordinary film. In this test, metal film shows a re¬ flection factor 12 per cent higher than cellulose film. Anxiety was expressed about the possible noise that metal film might make in its passage through the machine. The demonstration proved that metal lilm is just as silent as the standard film. The reason for this is that the film does not shrink or stretch, and passes through the sprockets with me¬ chanical precision. Emulsion Character The important questions from the vari¬ ous laboratories center around the char¬ acter of the emulsion and the processes of printing and finishing. A positive print is made on a metal film with the same machine and in the same manner as a positive print on cellulose film. The negative is brought into contact with the sensitized metal and exposed to the source of light. The printing time on metal film for any given emulsion is less than for ordinary film. Developing is more rapid than usual, and the time for fixing and washing is about half that ordinarily required. The drying economy is the most remarkable of all. The film may be passed through a drying cabinet at temperatures as high as 450 degrees F. At this temperature the film will dry in 2V2 minutes. Emul¬ sions on metal may have the same photo¬ graphic values as those used on cellu¬ lose. Where metal film is required as a negative, the exposure time in the camera and the general photographic technique is the same as usual. The de¬ veloping, fixing, washing and drying of a metal film negative may be done in one-third the usual time. The outstanding superiority of a metal film negative is the unusual absence of grain, coupled with positive permanence and practical indestructibility. Any Type Emulsion The metal negative must be printed by optical printing. When prints on both sides of the metal are required, a standard Debrie printer may be used for this purpose. If this type of printer is not available, both sides of the film may be printed in a standard machine, and the whole then developed. Care should be exercised to keep the emulsion sur¬ faces from scratching or abrading while in a wet condition. Any type of photographic emulsion may be coated upon our metal film. The essential physical requirement is the treatment of the emulsion together with the treatment of the metal base. This includes the necessary reduction of the interfacial tension in the emulsion and the rendering of the metal surface com¬ patible with such an emulsion. The advantages of metal film from the February, 1939 • American Cinematographer 59