A/D Converter - A device that converts analog information (a photograph or video frame) into a series of numbers that a computer can store and manipulate. All digicams use an A/D converter, the higher the bit rate the better the output. Modern hi-res digicams employ a 12-bit or 14-bit A/D to increase the dynamic range (range of light from highlight to shadow).
AA cell - In the digicam world this refers to the most common power source, the AA-size battery. See also "NiCd" and "NiMH".
AA Filter - Most digital SLR cameras employ a Low Pass Filter (LPF) or Anti-Aliasing (AA) filter in front of the imager to help eliminate color aliasing (moire) problems.
AC Power - Running your digicam off the wall outlet power rather than by battery power. Usually means purchasing optional AC power adapter.
Add-On Lens- Some lenses have filter threads on the front edge that allow you to mount an auxiliary wide angle or telephoto lens in addition to the standard lens.
AE - Auto Exposure, a system for automatically setting the proper exposure according to the existing light conditions. The most common types of AE systems:
1. Programmed where the camera picks the best shutter speed and aperture automatically
2. Program Shift same as Programmed plus the user can "shift" to other combinations of aperture and shutter speed values
3. Aperture Priority, the user chooses an aperture value and the shutter speed is automatically determined by lighting conditions
4. Shutter Priority, the user chooses a shutter speed and the aperture is automatically determined by lighting conditions
AE Lock - The ability to hold the current exposure settings and allow you to point the camera elsewhere before capturing the image. This is usually accomplished by half-pressing the shutter button and keeping it at that position until you're ready to capture the image.
AF - Auto Focus. A system that automatically focuses the camera lens.
Aliasing - An effect caused by sampling an image (or signal) at too low a rate. It makes rapid change (high texture) areas of an image appear as a slow change in the sample image. Once aliasing occurs, there is no way to accurately reproduce the original image from the sampled image.
Algorithm - A mathematical routine that solves a problem or equation. In imaging, the term is usually used to describe the set of routines that make up a compression or color management program.
Angle of View - The angle of view is calculated by the focal length of the lens and the size of the image sensor. Consumer digicam focal lengths are usually stated in terms of their 35mm film equivalents. For digital SLR cameras with interchangeable lenses it's more difficult as different cameras have different size sensors.
Anti-aliasing - The process of reducing stair-stepping by smoothing edges where individual pixels are visible.
Anti-Shake - Konica Minolta's "Anti-Shake" feature is the mechanical shifting of the imager to compensate for camera movement and minimize blurring at lower shutter speeds. Putting this type of image stabilization in the camera body of a dSLR means that it doesn't have to built into the lenses and therefore it makes them lighter and less expensive. See also "Optical Image Stabilization"
Aperture - The lens opening formed by the iris diaphragm inside the lens.
Aperture Priority AE - Exposure is calculated based on the aperture value chosen by the photographer. This allows for depth of field (DOF: Range of focus) control - large aperture = shallow DOF and a small aperture = deep DOF.
Archive - A collection of data in long-term storage.
Artifact(ing) - Misinterpreted information from a JPEG or compressed image. Color faults or line faults that visibly impact the image negatively.
Aspect Ratio - The ratio of horizontal to vertical dimensions of an image. The most common aspect ratio in digicams is 4:3 so that images "fit" properly on computer screens (800x600, 1024x768, 1280x1024) and standard TV screens. Many cameras offer a 3:2 mode so that you can print "perfect" 4x6-inch prints with no cropping necessary. There is also now the 16:9 mode on Panasonic and other digicams for viewing on the new widescreen HD TV displays.
Aspherical Lens - A lens whose edges have been flattened so that it is not a perfect sphere, produces a superior image.
Automatic Exposure - The camera automatically adjusts the aperture or shutter speed or both for the proper exposure.
Autofocus - The camera lens focuses automatically, usually when the shutter release is half-pressed.
AVI - Movie clip in Windows' AVI format. See "Movie clip"
AWB - Automatic White Balance. A system for automatically setting the white balance in today's digital cameras. See also "White Balance"
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