Additive color - The method of producing different hues by combining light. Three primary colors added together in equal proportions gives white light. Only a handful of additive color processes have ever been used significantly in photography. The most recent is Polachrome instant slide film, a black-and-white emulsion sandwiched to a screen of fine lines in the three primary colors. These give the color effect, but the drawbacks are a dense image (more murky than conventional slides) and the limited enlargement possible because of the screen lines.
