Active D-Lighting A camera setting that preserves highlight and shadow details in a high-contrast scene with a wide dynamic range.
AE See Autoexposure.
AF See Autofocus.
AF-assist illuminator An LED light that’s emitted in low-light or low-contrast situations. The AF-assist illuminator provides enough light for the camera’s autofocus to work in low light.
ambient lighting Lighting that naturally exists in a scene.
angle of view The area of a scene that a lens can capture, which is determined by the focal length of the lens. Lenses with a shorter focal length have a wider angle of view than lenses with a longer focal length.
aperture The opening of a lens, similar to the iris of an eye. The designation for each step in the aperture is called the f-stop. The smaller the f-stop (or f-number) is, the larger the opening of the aperture. Higher f-numbers designate smaller apertures and let in less light. The f-number is the ratio of the focal length to the aperture diameter.
Aperture-priority auto An exposure mode in which you choose the aperture and the camera automatically adjusts the shutter speed according to the camera’s metered readings. Aperture-priority auto is often used to control depth of field.
aspect ratio The ratio of the long edge of an image to the short edge as printed, displayed on a monitor, or captured by a digital camera.
Autoexposure (AE) A camera mode that selects the aperture and/or shutter speed according to the camera’s built-in light meter. See also ...