GLOSSARY^211
resolution The sharpness of an image that’s measured in dots per inch (dpi) for printers and pix-
els per inch (ppi) for scanners, digital cameras, and monitors. The higher the dpi or ppi, the greater
the resolution.
resolution, interpolated A process that enlarges an image by adding extra pixels whose color
values are calculated from the values of the surrounding pixels.
RGB The acronym for red, green, and blue, which are the primary colors of light and also the
color model used for television, digital cameras, and computer monitors.
rule of thirds A rule in composing pictures that divides the frame into nine equal areas.
The main objects in the photos should be aligned along one of the lines or at an intersection.
S
saturation The amount of color in a specific hue. More saturation makes the colors appear more
vivid, whereas less saturation makes the colors appear muted. See also brightness and hue.
Secure Digital memory A memory card about the size of a postage stamp. It weighs about
two grams; available with storage capacities as high as 4GB.
sharpening A function in digital darkroom software, some cameras, and some scanners that
increases the apparent sharpness of an image by increasing the contrast of pixels along the borders
between light and dark areas in the image.
shift-tilt lens A lens with a mechanism that lets part of it shift in any direction parallel to the cam-
era’s image plane or tilt in any direction. Shifting the lens is used to correct perspective distortions,
particularly in architectural photography, caused when the camera is tilted, for example, at ground
level to take in the entirety of a tall building. Tilting the lens changes the depth of field area that’s in
focus so that it is on a diagonal in relation to the camera, allowing the photographer to bring into
focus more elements that are stretching away from the camera.
short lens A wide-angle lens that includes more of the subject area.
shutter The device in a camera that opens and closes to let light from the scene strike the image
sensor and expose the image. See also diaphragm.
shutter speed The length of time during which the camera shutter remains open. These speeds
are expressed in seconds or fractions of a second, such as 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30,
1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, and 1/8000. Each increment is equal
to one full f-stop. Increasing the speed of the shutter one increment, for example, reduces the amount
of light let in during the exposure by half, so the lens aperture would need to be opened one f-stop to
produce an exposure with the same tonal values as the exposure made with the original shutter
speed setting.