Metallic-Salt Track on Ansco 16-MM Color Film
John L. Forrest · Journal of the Society of Motion Picture Engineers · 1949
In 16-mm Ansco color motion picture film the silver is removed from the image, leaving dye in the three layers. The combination (maximum density) of the subtractive colors has a visual density of about 3, which is sufficient to produce good screen contrast. The maximum density, while being visually opaque, has a transmission band in the near infrared in the region of 8000 angstrom units, which is the most sensitive region of the cesium-type phototube. While for many purposes this may not be objectionable, it can be overcome by differentially processing the film so that the sound-track modulations are opaque to red light without affecting the dye picture area. This paper describes a method by which differential treatment of the sound track area can be accomplished.