A natural-color film that fits amateur cameras and projectors of standard sixteen-millimeter size now permits home movie makers to take color pictures of professional quality. No special filters or other auxiliary devices are required. Pictures may be taken indoors or outdoors, exactly as in black-and-white photography; the only difference whatever, as far as the picture maker is concerned, is that a slightly larger stop - F/8 instead of F/11, for example - is used to admit more light.
To separate the various hues in a scene, other single-film processes resort to such devices as color gratings, prismatic ridges, or microscopic tinted grains on the surface of the emulsion. The new film dispenses with all these, and can be magnfied indefinitely without the appearance of grains or streaks. So translucent are the images obtained, that a low-power projector is adequate to give brilliant, glowing colors.
A "sandwich" of five gossamer-thin layers, with a combined thickness hardly greater than that of a standard emulsion, constitutes the coating of the new film. The layers include an emulsion sensitive to blue light only, with which is incorporated a yellow stain to serve as a color filter; a separating layer or gelatin for mechanical purposes; a green-sensitive emulsion; a dyed gelatin color filter; and a red-sensitive emulsion. How the three emulsions register the three primary colors of the subject and combine them in single natural-color pictures is shown in the diagram.
Applying so thin a sandwich of layers to a film is a feat in itself, but even more remarkable is the method of dyeing up the images in their proper colors. Sent to the manufacturer for finishing, the film is run through a series of intricate and delicate chemical processes that dye the front, middle, and read images of each "frame" selectively. Each image receives its own color, and no dye strays, despite the microscopic distances that separate one layer from another. The final treatment removes all traces of the original silver imgaes produced by development, leaving the natural-color picture in the transparent dyes.
Drawing at left shows how the new color film works. The five layers are combined in a thin coating. Above, magnified cross section of film showing emulsion layers contrasted with film base
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