Natural color film : what it is and how to use it (1937)

DEFINITION OF COLOR FILM mentary to the filter used, we shall be able to make photographs in colors which bear a close similarity to the original. Since a motion picture is projected by transmitted light it can readily be understood that there are two ways of getting a colored picture on the screen. The first is to recombine our three primary-color images in a fully colored print, so that, starting with the white light of the projector, the print itself removes from the beam all of the color frequencies not desired to make up any given portion of the picture. This is known as the subtractive method and is the basic nature of Kodachrome. The second method utilizes a simple black and white print, and places appropriate filters between the film and the screen, virtually adding color to the shadow of the black and white image. This is known as the additive method, of which Kodacolor was an example. In subtractive color-processes, the formation of color depends on the principle followed by nature. Naturally occurring substances are those which absorb part of the white light falling upon them. Thus a red substance is one which absorbs blue and green, so that when it is illuminated by white light, everything but the red is absorbed. A substance which is blue-green in color absorbs the red light. Blue-green is said to be complementary of red because when added together they make white. It is usual to speak of the compound complementary as a ''minus" color. Thus the peculiar bluish-green which results from the removal of red from white is often called ' ' minus-red ' ', as this is a more exact term than "blue-green". On the contrary, however, we should not call red "minus blue — 21 —