Radio age research, manufacturing, communications, broadcasting, television (1941)

The Story of 16mm. Sound From Its Start in This Field in 1931, RCA Has Scored Many "Firsts" in Methods and Equipment SIXTEEN years ago, the Radio Corporation of America intro- duced the first 16mm sound film projector. Since that date, RCA, through its 16mm Motion Picture Equipment Section, has carried out continuous development work in its laboratories out of which has come the present perfected 16mm sound projector as it is known to the in- dustry today. The first problem faced in the early Thirties, that of putting sound on the narrow film, only %" in total width, was considered in- superable but RCA solved it. From that starting point, the company went on to score most of the signifi- cant "firsts" in the 16mm industry. The first 16mm sound projector was developed by RCA in 1931. Behind it lay years of pioneering effort aimed at solving the many problems — optical, photographic, electronic and mechanical — which plagued photographic sound record- ing. RCA's first innovation was 16mm film with one row of sprocket holes which reserved the other side of the film for the sound track. In cooperation with the Eastman Com- pany, the film was presented for standardization to the Society of Motion Picture Engineers and after being adopted as the American standard, was later made world standard. Film Speed a Problem The small area available for sound on 16mm film was further complicated by the fact that 16mm film runs at only 36 feet per minute against 90 feet per minute for 35mm film. This slower speed fur- ther reduced the linear space avail- able on the 16mm film to only 40 percent of that on 35mm film. RCA's answer, in 1928, was a revolutionary new "dry" galva- nometer, part of a greatly improved optical sound recording system. Outstanding feature of the new galvanometer was a mirror fifteen times larger than previously used on sound film recording systems. By W. W. Watts Vice President in charge of Engineering Products Dept., RCA Victor Division The new mirror cast light of much greater intensity and made possible an optical system of high resolving power. This, in effect, was the finer "paint brush" necessary to get good resolution of the hair-fine lines on the tiny 16mm track. The greater light intensity also per- mitted the use of finer-grain film. resulting in even better I'esolution. In addition, RCA engineers de- veloped, at about this same time, a magnetic film drive for sound re- cording which provided smooth and oscillation-free passage of the film through the recording light. A corresponding improvement in the reproduction of sound in the pro- jector was also made possible by RCA's development of the "rotary stabilizer" which passed the film at smooth and steady speed through the projector, ironing out speed variations which previously had made all pianos sound out of tune and introduced Hawaiian guitar effects into all music. Grain in Film Caused Noise A source of interfering noise was graininess in the film texture intensified by dirt and imperfec- tions on the sound track which registered as hissing, crackling and "frying" noises. RCA engi- neers blanked out this static and chalked up a notable "first" in noise reduction by devising an automatic biasing system which, during low- level passages, keeps the clear area of the track no wider than needed at the moment to record the sound on the nim. Reproducing sound from a film track requires an intense beam of G. A. DEL VALLE, RCA DESIGN ENGINEER, AND 0. V. SWISHER, GENERAL MANAGER OF 16MM. ACTIVITIES, COMPARE THE 1931 MODEL PROJECTOR (left) WITH THE LATEST SOUND FILM UNIT. [30 RADIO AGE]