Acquire: The opening up and importing of files into a given software application. The term is applied differently with in different types of software. With imaging software it is most often done through a twain interface or plug-in mini-application.

AE: Auto Exposure is a system for automatically setting exposure by choosing a shutter speed and aperture value according to the current light conditions. This is commonly referred to as "Auto Mode", and is the best setting for most conditions. It enables the photographer to concentrate on the subject while the camera adapts to optimum performance for the environment. 

Aperture: The opening in the lens that controls how much light hits the camera's image sensor. 
The aperture is an iris in the lens that can be opened or closed to allow more or less light into the camera. The smaller the aperture the less light it allows to enter through the lens. This is one of the ways a camera regulates exposure.

Aperture Priority: A larger aperture (opening) allows more light for a brighter image. This is very useful when taking pictures at night or in a dark room. Reducing the aperture can control light in environments that may be too bright. During Aperture Priority Mode on Toshiba Digital Cameras the Shutter and Flash are automatically set to optimize performance.

Artifact(ing): Misinterpreted information from a JPEG or compressed image. Color faults or line faults that visibly impact the image negatively.

Artificial light: Light from a man-made source, usually restricted to studio photo lamps and domestic lighting.

ASCII: American Standard Code for Information Interchange (ASCII) is an ANSI binary-coding scheme consisting of 128 seven-bit patterns for printable characters and control of equipment functions. ASCII is the basis for information exchange between many computer systems.