Sabattier effect:  A partial reversal of tones that occurs when film or paper is re-exposed to light during development.  Commonly called solarization.

Safelight:  A light used in the darkroom during printing to provide general illumination without giving unwanted exposure.

Selective-contrast paper See variable-contrast paper.

Sharp:  Describes an image or part of an image that shows crisp, precise texture and detail.  Opposite:  blurred or soft.

Sheet film:  Film that is cut into individual flat pieces.  Also called cut film.

Short lens A lens whose focal length is shorter than the diagonal measurement of the film with which it is used.  The angle of view with this lens-film combination is greater at a given distance than the angle seen by the human eye.  Also called a wide-angle or wide-field lens.

Short lighting A portrait lighting setup in which the main source of light illuminates the side of the face partially turned away from the camera.  Also called narrow lighting.

Shutter A mechanism that opens and closes to admit light into a camera for a measured length of time.

Shutter-priorityA mode of automatic exposure in which the photographer selects the shutter speed and the camera sets the aperture that will produce the correct exposure.

Silhouette:  A scene or photograph in which the background is much more brightly lit than the subject.

Silver halide The light-sensitive part of common photographic emulsions; the compounds silver chloride, silver bromide, and silver iodide.

Single-lens reflex A camera in which the image formed by the taking lens is reflected by a mirror onto a ground-glass screen for viewing.  The mirror swings out of the way just before exposure to let the image reach the film.  Abbreviated SLR.

Slave:  An electronic flash unit that fires when it detects a burst of light from another flash unit.

Slave eye:  A sensor that detects light to trigger a slave flash unit.

Slide:  1.) A transparency (often a positive image in color) mounted between glass or in a frame of cardboard or other material so that it may be inserted into a projector.  2.) A protective cover that is removed from a sheet film holder when film in the holder is to be exposed.  Also called dark slide.

Slow:  Describes 1.) A film or paper that is not very sensitive to light; 2.) A lens whose widest aperture is relatively small; 3.) A long shutter speed.  Opposite:  fast.

SLR:  See single-lens reflex.

Sodium thiosulfate:  The active ingredient in most fixers.

Soft:  1.) Describes an image that is blurred or out of focus.  Opposite:  sharp.  2.) Describes a scene, negative, or print of low contrast.  Opposite:  hard or high contrast.  3.) Describes a printing paper emulsion of low contrast, such as grade 0 or 1.

Software:  The programs, such as Adobe Photoshop, used to direct a computer to make desired changes in a digital image or other digital file.

SolarizationA reversal of image tones that occurs when film is massively overe3xposed.  See also Sabattier effect.

Speed:  1.) The relative sensitivity to light of film or paper.  2.) The relative ability of a lens to admit more light by opening to a wider aperture.

Spot:  To remove small imperfections in a print caused by dust specks, small scratches, or the like.  Specifically, to paint a dye over small white blemishes.

Spotlight An electric light that contains a small, bright lamp, a reflector, and often a lens to concentrate the light.  Designed to produce a narrow beam of bright light.

Spot meter A reflected-light exposure meter with a very small angle of view, used to measure the brightness of a small portion of a subject.

Stereograph A pair of photographs taken side by side and seen separately by each eye in viewing them through a stereoscope.  The resulting image looks three-dimensional.

Stock solution A concentrated chemical solution that is diluted before use.

Stop 1.) An aperture setting on a lens.  2.) A change in exposure by a factor of two.  One stop more exposure doubles the light reaching film or paper.  One stop less halves the exposure.  Either the aperture or the exposure time can be changed.  3.) See stop down.

Stop downTo decrease the size of a lens aperture.  Opposite:  open up.

Strobe:  1.) Abbreviation of stroboscopic.  Describes a light source that provides a series of brief pulses of light in rapid succession.  2.) Used loosely to refer to any electronic flash.

Subtractive color:  A way to produce colors by mixing dyes that contain varying proportions of the three subtractive primary colors-cyan, magenta, and yellow.  Each dye subtracts its color from white light, leaving a balance of colored light.  Dyes that absorb all wavelengths of light produce black.

Supplementary lens A lens that can be added to a camera lens for close-up work.  It magnifies the image and permits focusing closer than normal to an object.

Sync cord:  An electrical cord connecting a flash unit with a camera so that the two can be synchronized.  Pronounced “sink”.

Synchronize:  To cause a flash unit to fire at the same time as the camera shutter is open.

Synchro-sun:  A way to use flash lighting as fill light in a photograph made in direct sunlight.  The flash lightens the shadows, decreasing the contrast in the scene.