lens—A piece, or combination of pieces, of glass or other transparent material shaped to form an image by refraction.

lens, coated—A lens coated to reduce light reflection from its surfaces and for selectively absorbing light of a particular wave length (color) so as to prevent it from passing through the lens.

lens, narrow-angle—A lens whose focal length is equal approximately to twice the diagonal of the format. See also angle of coverage.

lens, normal-angle—A lens whose focal length is equal approximately to the diagonal of the format. See also angle of coverage.

lens, wide-angle—A lens whose focal length is equal approximately to one half the diagonal of the format. See also angle of coverage.

lens calibration—See calibration, camera.

lens distortion—See distortion. See also aberration of light [OPTICS].

lens element—One lens of a complex lens system. In a photographic lens, one can also distinguish between a front and rear element.

lens law—The equation relating the distance from a point in object-space to the front nodal point of an optical system, the distance from the corresponding point in image space to the rear nodal point and the focal length of the system.

lensatic compass—See compass, lensatic.

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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