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The Movietone sound system is an optical sound-on-film method of recording sound for motion pictures that guarantees synchronization between sound and picture. It achieves this by recording the sound as a variable-density optical track on the same strip of film that records the pictures. Although sound films today use variable-area tracks, any modern motion picture theater (excluding those that have transitioned to digital cinema) can play a Movietone film without modification to the projector (though if the projector has been fitted with red LED or laser photocells, the reproduction quality from a variable density track will be significantly impaired). Movietone was one of four motion picture sound systems under development in the U.S. during the 1920s, the others being DeForest Phonofilm, Warner Brothers' Vitaphone, and RCA Photophone, though Phonofilm was primarily an early version of Movietone. ==History== As a student Theodore Case became interested in the use of modulated light to carry speech, and in 1914 set up a laboratory to study the photo-electric properties of materials. He developed the ''Thalofide cell'', a sensitive photocell, which was used as part of an infra-red communication system by the U.S. Navy during, and for some years after, WW1. In 1922 Case and his assistant Earl I. Sponable turned their attention to "talking pictures". In that same year Case was approached by Lee de Forest who had been attempting since 1919 to create an optical soundtrack for motion picture film in a system he called ''Phonofilm''. De Forest was having little success and turned to Case for help, so from 1922 until 1925 Case and de Forest collaborated in the development of the Phonofilm system. Amongst other Case inventions Case contributed the Thalofide photocell and also the ''Aeo-light'', a light source that could be readily modulated by audio signals and was used to expose the soundtrack in sound cameras. In 1925, however, Case ended his relationship with de Forest due in the main to de Forest's tendency to claim the entire credit for the Phonofilm system for himself despite the fact that most of the critical inventions had come from Case. Documents supporting this, including a signed letter by De Forest that states that Phonofilms are only possible because of the inventions of Case Research Lab, are located at the Case Research Lab Museum in Auburn, New York.〔(Case Lab Museum website )〕 In 1925, therefore, Case and Sponable continued the development of their own system, now called ''Movietone''. From 1924 onwards Sponable had turned his attention to the design of single-system cameras, in which the sound and picture are recorded on the same negative. He asked Bell & Howell to modify one of their cameras to his design, but the results were unsatisfactory. Consequently the Wall machine shop in Syracuse, New York was asked to rebuild this camera and the results were much improved. Subsequently many single-system 35mm cameras were produced by Wall Camera Corporation, which much later produced the three-film Cinerama cameras. Wall initially converted some Bell & Howell Design 2709 cameras to single-system, but most were Wall designed and produced. Single-system cameras were also produced by Mitchell Camera Corporation during World War II for the U.S. Army Signal Corps, although these cameras were quite rare. Partly as a result of the single system experiments, the aspect ratio of approximately 1.19:1 that is created by printing an optical soundtrack on top of the 35mm full aperture became known colloquially as the "Movietone ratio". It was used extensively by Hollywood and European studios (apart from those that adopted sound-on-disc) between the late 1920s and May 1932, when the Academy Ratio of 1.37:1 was introduced to restore the effective shape of the silent frame. The 1950s brought the first 35mm kinescope camera with sound-on-film rather than separate, from Photo-Sonics, with a Davis Loop Drive mechanism built within the camera box. This camera was essential for TV network time-shifting in the years before Videotape. The sound galvanometer was made by RCA and was designed for good to excellent results when the kinescope negative was projected, thereby avoiding making a print before the delayed replay. The Davis mechanism was a Western Electric development. After the split with de Forest, Case adopted a revised position for the projector soundhead, which was now placed below the picture head, with a sound-picture offset of 14 ½ inches (368 mm) (which is close to the present day standard), rather than being placed above the picture head as had been the phonofilm practice. Case also adopted the 24 frames/sec speed for Movietone, bringing it in line with the speed already chosen for the Western Electric Vitaphone sound-on-disc system, and thus establishing 24 frame/sec as the standard speed for all sound films, whether sound-on-disc or sound-on-film. With a few exceptions this has remained the standard speed for professional sound films ever since.〔Earl I. Sponable, "Historical Development of Sound Films", The Journal of the Society of Motion Picture Engineers (April 1947), Vol. 48, No. 4〕〔Edward Kellogg, "History of Sound Motion in Pictures", The Journal of the Society of Motion Picture Engineers (June 1955), Vol. 64, p. 295〕 At this point, the Movietone system was adopted by the AMPAS as the Academy's standard. It and the later RCA Photophone system were interchangeable in most respects. See RCA Photophone for technical details and lists of the industry adopters. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Movietone sound system」の詳細全文を読む スポンサード リンク
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