The art of sound pictures (1930)

248 THE ART OF SOUND PICTURES considerable capital is attempting to perfect and put on the market a process of this sort. «-^The motion picture film which carries three successive frames containing red, green, and blue color values is, nevertheless, black and white. The color values in the different frames are latent, and the films are not themselves colored. The only difference which the naked eye can detect in the three successive frames is a difference in shading between different parts of the picture. A red rose in the red frame on the film might appear very light, with its leaves somewhat darker. In the green frame of the same picture, the rose might be darker, and its leaves lighter. And so on. But these differences in development of the film will again give the original colors when exposed behind the color filter of the color that was originally used in taking the picture. A negative film which is prepared in such a way that it is differentially or selectively sensitive to different colored lights is called a panchromatic film. This type of film may now be obtained without difficulty. Commercially, this type of latent color record on the film is very much more economical and advantageous in every way than a film which is itself colored. The chief reason for this commercial advantage is that panchromatic film can be developed and printed in an ordinary film laboratory without any additional processes or special treatments. If the film itself has to be colored, additional dye processes or chemical conversion processes must be carried out, which require considerable extra expense and time. In the motion picture business, the time element is often more important than are a few extra thousand dollars in the cost of development. A news reel, for