Aplanat

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Aplanat

 

a photographic objective with an optical system consisting of two achromatic lenses placed symmetrically about the diaphragm. The aplanat is free from spherical aberration, chromatic aberration, and distortion; but astigmatism, though severely attenuated, remains present. Because of its simplicity of design and loose mounting requirements, the aplanat lends itself readily to use as a universal lens with a relative aperture from f/8—rarely f/5 (for portrait work and group photographs)—to f/16 (as a wide-angle lens). With the appearance of anastigmats, aplanats lost their significance and are now produced in small quantities.

REFERENCE

Lapauri, A. A. Fotograficheskaia optika. Moscow, 1955.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.