pincushion distortion

irregular image produced when axial magnification is greater than peripheral magnification. See: Petzval surface.

Farlex Partner Medical Dictionary © Farlex 2012

pin·cush·i·on dis·tor·tion

(pin'kush-ŭn dis-tōr'shŭn)

Irregular image produced when axial magnification is greater than peripheral magnification.
See: Petzval surface

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

distortion

Aberration of an optical system resulting in an image which does not conform to the shape of the object, somewhat resembling the image viewed through a cylindrical lens. This is due to an unequal magnification of the image. Distortion can be barrel-shaped (barrel-shaped distortion) in which the corners of the image of a square are closer to the centre than the middle part of the sides; or pincushion (pincushion distortion) in which the corners of the image of a square are farther from the centre than the middle part of the sides (Fig. D10). Example of barrel-shaped distortion: a square object seen through an uncorrected negative spectacle lens. Example of pincushion distortion: a square object seen through an uncorrected positive spectacle lens. See correction; fisheye lens; sine condition.

Fig. D10 Distortion (O, object; A, pincushion distortion; B, barrel-shaped distortion)

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References in periodicals archive

Examining the Nikon we noted no astigmatism, curvature of field, rolling distortion, or pincushion distortion.

As is the nature of the beast the image did degrade towards the edges and we detected some curvature of field and pincushion distortion. During low-light testing those big 42mm lenses went to work and allowed us to discern all the way down to the 4 percent mark.

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However I did note a small amount of pincushion distortion. Putting it up to a ZTP chart at 50 yards, I could cleanly resolve down to the No.

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All the eyepieces magnified more powerfully near the edge than near the center, producing so-called pincushion distortion; test squares showed concave sides.

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All the eyepieces suffered from pincushion distortion, which could easily be detected about a third of the way to the edge of the field.

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