ABSTRACT
A filmstrip consists of two layers: a base and the emulsion. The emulsion takes up 3 to 10 percent of the total thickness of a filmstrip. The emulsion of black-and-white film consists of a gelatin that contains grains of silver halide. When light is reflected from the scene in front of the camera, a chemical reaction causes the crystals to form a pattern that produces a latent corresponding image. The emulsion of color film is approximately three times thicker than the emulsion of black-and-white film because it also consists of three layers of dye that are sensitive to a primary color (red, blue, and yellow). The emulsion side of a filmstrip absorbs moisture and can be scratched off quite easily. The base side of the filmstrip is stiffer and less vulnerable. The material of the base—also called the film’s carrier—has changed over time: from nitrate (1989-1951) to acetate (since 1910) to polyester (since 1955). Along both sides of the film are sprocket holes that enable the film to be transported through cameras, projectors, and other equipment. One single frame takes up four sprocket holes. With sound film, the soundtrack (optical or magnetic) is on the left side between the frames and the sprocket holes. Digital soundtracks might be next to the optical track as a dotted line (DTS) or as a pattern of dots in between the sprocket holes (SRD).
