SENSITOMETER An instrument with which a photographic emulsion is given a graduated series of exposures to light of controlled spectral quality, intensity, and duration.

SHADOW General term for the thinner areas of a negative or the darker areas of an original.

SHOT (1) Motion picture. The most basic unit of a film; a single scene; the continuous action occurring from the time the camera is turned on to the time it is turned off. (2) Still picture. A single exposure or photograph.

SHUTTER, BETWEEN-THE-LENS A shutter whose blades operate between two elements of the lens, as differentiated from the focal plane or behind-the-lens shutters. Sometimes applied to an iris diaphragm whose blades operate between lens elements.

SHUTTER, FOCAL-PLANE A shutter located near the focal plane and consisting of a curtain with a slot that is pulled across the focal plane to make the exposure. The width of the slit and the speed it is moved determine the duration of the exposure.

SHUTTER RELEASE A device to actuate a camera shutter.

SHUTTER SPEED The length of time that light is permitted to act upon film or paper as a result of the shutter having opened and closed.

SILHOUETTE An art term for the outline of a form in black or white that is offset by a background of the contrasting color. (PIA)

SILVER HALIDE A compound of silver and one of the following elements known as halogens: chlorine, bromide, iodine, and fluorine. (NMA)

SLANT TRACK Same as helical scan.

SODIUM HYDROXIDE (CAUSTIC SODA, SODIUM HYDRATE), NaOH A deliquescent white material usually available as pellets, flakes, or sticks. Soluble in water with the liberation of heat. A very active accelerator used in high-energy developers. Concentrated solutions are quite caustic and will attack the skin, causing painful burns.

SODIUM THIOSULFATE (THIOSULFATE OF SODA, HYPO) Na2S2O35H2O Colorless crystals, very soluble in water. It is the principal constituent of most fixing solutions. It may be available in the anhydrous form.

SOFT (l) As applied to a photographic emulsion or developer, having a low contrast. (2) As applied to the lighting of a set, diffuse, giving a flat scene in which the brightness difference between highlights and shadows is small.

SOFT FOCUS An unsharp photographic image or a special lens or exposing technique by means of which it is produced. (PIA)