The international photographer (Jan-Dec 1935)

Eight The INTERNATIONAL PHOTOGRAPHER March, 1935 IP|11P|Pfll Fig. 1. Comparison of variable-width sound tracks on Kodacolor film and on standard film. |T is the purpose of this paper to present a brief account of work done in the development laboratory relative to the production of 16 mm. sound films in full color. The medium selected was the well-known Kodacolor process of color photography and projection, a true three-color additive process,1,2 by which excellent pictures may be made and projected in full natural color. Following extensive development in the 16 mm. sound picture field, during which means were worked out for producing 16 mm. recording from 35 mm. sound films, some attention was given to the matter of producing 16 mm. sound records on Kodacolor film. It was thought at the time that some peculiar effects might arise if the sound recording beam were passed through the longitudinally lenticular base of the film before the final formation of the image on the emulsion, as in the case of the picture. The lenticular film base would no longer permit the formation of a true optical-slit on the emulsion, but would produce a series of images, each separated from the other, formed by the several cylindrical lenses in the path of the beam. For instance, if a recording optical system images an optical slit upon an emulsion through a longitudinally lenticulated film base, the image that results will be a true image of the slit in the longitudinal plane, and a series of more or less sharp images of the exit pupil of the system in the transverse plane. And as the cutting edge of the recording beam advances and recedes across the cylindrical lenses there will be produced a series of more or less fully illuminated images of the exit pupil of the system in the transverse plane, according to the extent to which the individual lenses on the film base are filled with light. Thus, in recording in this fashion by the variable-width process, the recording image consists of a series of more or less brightly illuminated image element, rather than a uniformly illuminated image of continuously varying length. Fig. 1 shows the comparison between variable-width recording on standard film and on Kodacolor film when the emulsion is in the reverse position. It is seen that the blackened portion of the variablewidth negative will comprise a series of longitudinal strips of density, rather than a continuous field of density, and that the boundary between the clear and the blackened portions of the track will not be a smooth curve, but will comprise a series of more or less fully exposed images * Presented at the Spring, 1934, Meeting at Atlantic City, N. J. ** RCA Victor Company, Camden, N. J, Sixteen -Millimeter Sound Pictures in Color* By C. N. Batsel and L. T. Sachtleben** SUMMARY — The nature of a variable-width sound track on longitudinally lenticulated color films is discussed, and the optical reduction of 35 mm. subtractive color subjects to 16 mm. film by the Kodacolor process is described. From the Journal of the S. M. P. E. of the exit pupil, in the transverse plane. Or, more simply, the boundary presents a serrated or step-like appearance where it crosses the lenticulations. This was a situation quite different from that encountered in usual variable-width practice, and it was felt that distortions of a more or less troublesome nature might arise from it. A single-film, 16 mm. sound camera was chosen to test the feasibility of recording sound on Kodacolor film. The camera was constructed for normal black-and-white picture work with the recording system focused directly upon the emulsion in the obverse position. With Kodacolor film the emulsion was in the reverse position, making it necessary to refocus the recording system before a recording could be made. The original test recording was made on August 9, 1932. The sound record was very successful and definitely demonstrated the feasibility of recording sound on this film by the variable-width process, with the emulsion in the reverse position. It was found that no distortion of a serious nature occurred due to the use of Kodacolor film with longitudinal lenticulations. Pursuant to the successful recording of sound on Kodacolor film in the single-film, 16 mm. sound camera, it was believed that subtractive color subjects on 35 mm. film should be optically reducible to 16 mm. film by the Kodacolor process, using an optical system similar to that employed in Kodacolor photography with the 16 mm. camera. The first test was made in a crude way using a projector fitted with a two-inch Kodacolor projection lens as a camera. The projector was mounted in a lighttight box and focused on a white card, upon which was projected an image of a frame from a 35 mm. Technicolor print. A strip of raw Kodacolor film was placed in the projector, exposed and reversed, with the result that a fairly promising image was obtained when the film was reprojected. Following this, an optical-reduction step-printer was equipped with the necessary optics to permit printing directly from a 35 mm. Technicolor film to 16 mm. Kodacolor film. This optical system was essentially the one used in Kodacolor projection, with a three-color filter in front of the printing lens, and a negative lens at the 16 mm. film to produce a virtual image of the filter of the proper size at the proper distance from the film. The first system was improvised from such optics as were available in the laboratory, and the pictures obtained exhibited marked color dominants at the margins, due to the insufficient speed of the printing lens and the consequently diminished size of the filter image. Nevertheless, the results were remarkably promising. Later, a lens of sufficient speed was obtained to permit the required 3:1 ratio between the distance from the film to the filter image, and the total width of the filter image ; with the result that a great improvement was effected in the color-balance, and the color dominants at the edges (Turn to Page 20) Please mention The International Photographer when corresponding with advertisers.