A
lens surface with more than one radius of curvature
(i.e., the surface does not form part of a sphere). The aspherical elements of a
lens help compensate for many lens aberrations common in simpler lens designs.
Aspherical elements are particularly important for wide-angle lenses, since they
are prone to distortion.
See "A
Quick Guide to Digital Cameras" in the
Quick Reference section of
Webopedia.
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