samples per inch (spi): The number of pixels both horizontally and vertically in each squared inch scanned by a scanner or recorded by a digital camera.

scanner: A device that captures an image of a piece of artwork, a slide, or a negative, and then converts it to a digitized image or bitmap that the computer can handle.

scene modes: Digital camera’s special picture-taking modes that are designed to automatically set all the available focus and exposure controls for a certain type of subject matter.

self-timer: Mechanism that delays the opening of the shutter for some seconds after the release has been operated.

shoulder stock: Devices modeled after rifle stocks that brace the camera lens into your shoulder, thus helping hold it steady.

shutter: The device in a camera that opens and shuts to allow light into the camera.

shutter button: The button on your digital camera that you press to take a picture.

shutter speed: The length of time that the camera shutter remains open, thereby allowing light to enter the camera and expose the photograph.

shutter-priority autoexposure: A semi-automatic exposure mode in which the photographer sets the shutter speed and the camera selects the appropriate aperture.

single auto-focus: A setting in which the camera focuses on a single object.

slave: An accessory flash unit that supplements the main flash, usually triggered electronically when the slave senses the light output by the main unit.

SLR (single-lens reflex) camera: A type of camera that includes interchangeable lenses, manual focus and exposure controls, and connections for an external flash.

snoot: A tube-like device that focuses the flash’s light to a very small area.

soft box: An attachment that mounts on the head of the flash and extends out about 6 to 8 inches, with a frosted white panel at the end, which softens the light.

spot metering: Metering mode that bases exposure on light in the center of the frame only.

stitch: Creating a panorama from multiple images by overlapping those images.

strobe: Another name for an electronic flash unit, especially when it's used as the only source of illumination.

subcompact: A type of digital camera that's small enough to fit comfortably in a shirt pocket.

super floppy: Removable storage devices; the best-known option is the Zip drive.

swivel mount: The part of a tripod to which the camera attaches that you can move to some degree.

sync connector: A special bracket that fastens to the tripod socket on the bottom of a digital camera; allows you to connect an external flash to your camera.