Nikon manual David Busch’s Nikon D7000 Guide to Digital SLR Photography

490 David Busch’s Nikon D7000 Guide to Digital SLR Photography

aspect ratio The proportions of an image as printed, displayed on a monitor, or cap- tured by a digital camera. The D7000’s movie feature, for example, includes options for HDTV’s 16:9 aspect ratio.

Autofocus A camera setting that allows the Nikon D7000 to choose the correct focus distance for you, based on the contrast of an image (the image will be at maximum con- trast when in sharp focus). The camera can be set for Single-servo Autofocus (AF-S), in which the lens is not focused until the shutter release is partially depressed, Continuous- servo Autofocus (AF-C),in which the lens refocuses constantly as you frame and reframe the image, and Automatic-autofocus(AF-A),in which the D7000 focuses using AF-S mode, but switches to AF-C mode if the subject starts to move. The D7000 can also be set for Manual focus. In Live View mode, your two choices are AF-S and AF-F.

backlighting A lighting effect produced when the main light source is located behind the subject. Backlighting can be used to create a silhouette effect, or to illuminate translucent objects. See also front lighting and side lighting.

barrel distortion A lens defect that causes straight lines at the top or side edges of an image to bow outward into a barrel shape. See also pincushion distortion.

blooming An image distortion caused when a photosite in an image sensor has absorbed all the photons it can handle so that additional photons reaching that pixel overflow to affect surrounding pixels, producing unwanted brightness and overexpo- sure around the edges of objects.

blur To soften an image or part of an image by throwing it out of focus, or by allow- ing it to become soft due to subject or camera motion. Blur can also be applied cre- atively in an image-editing program.

bokeh A term derived from the Japanese word for blur, which describes the aesthetic qualities of the out-of-focus parts of an image. Some lenses produce “good” bokeh and others offer “bad” bokeh. Some lenses produce uniformly illuminated out-of-focus discs. Others produce a disc that has a bright edge and a dark center, producing a “doughnut” effect, which is the worst from a bokeh standpoint. Lenses that generate a bright cen- ter that fades to a darker edge are favored, because their bokeh allows the circle of con- fusion to blend more smoothly with the surroundings. The bokeh characteristics of a lens are most important when you’re using selective focus (say, when shooting a por- trait) to deemphasize the background, or when shallow depth-of-field is a given because you’re working with a macro lens, with a long telephoto, or with a wide-open aperture. See also circle of confusion.

bounce lighting Light bounced off a reflector, including ceiling and walls, to provide a soft, natural-looking light.