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A
3x, 5x, 10x
- Denotes the focal length ratio of a zoom lens -
this is an optical, not digital zoom.
See also "Digital Zoom" below.
AA
- In the digicam world this refers to the most common
power source, the AA-size battery. See also "NiCd"
and "NiMH" and check here: NiMH Batteries/Chargers.
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. There are three types of AE systems:
- Programmed where the camera
picks the best shutter speed and aperture automatically.
- Aperture Priority, the user
chooses an aperture value and the shutter speed
is automatically determined by lighting conditions.
- 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.
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).
Anti-aliasing
- The process of reducing stair-stepping by smoothing
edges where individual pixels are visible.
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. (35mm slide frame is 3:2, TV 4:3, HDTV 16:9,
4X5 film 5:4)
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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