Optical distortion is a position-dependent change of image scale: a system fails to map object coordinates by one uniform magnification. It can bend the images of straight lines even when individual image points remain sharp.
Photographing a rectangular grid makes the effect concrete. When the radial image scale decreases toward the edge, the grid bows outward in the familiar barrel pattern; the opposite tendency produces a pincushion pattern. A calibrated coordinate mapping can correct geometry in a recorded image, but cannot recover detail already lost through blur, coarse sampling or clipping.
In optics, distortion refers to the deviation of an image from the ideal shape or proportions of the object that is being photographed or viewed through a lens system. Unlike other optical aberrations, such as spherical aberration or chromatic aberration, distortion specifically affects the geometry of the image rather than its sharpness or color fidelity.
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