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 (AE).
AF-assist illuminator An LED that is emits a beam 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 light Lighting that naturally exists in a scene.
angle of view The area of a scene that a lens can capture. The area 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, which is similar to the iris of the eye. The designation for each step in the aperture is called an f-stop. The smaller the f-stop (or f-number), the larger the opening of the aperture; higher f-numbers designate smaller apertures, letting 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. See also Autoexposure (AE), Programmed auto, and Shutter-priority auto.
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. The native ratio for the D5300 is 3:2 for still images and 16:9 for ...