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In geometric optics, distortion is a deviation from rectilinear projection; a projection in which straight lines in a scene remain straight in an image.It is a form of optical aberration that may be distinguished from other aberrations such as spherical aberration, coma, chromatic aberration, field curvature, and astigmatism in a sense that these impact the image sharpness without changing an ...
The perceptual barrel distortion is sufficiently small to be unnoticeable in everyday life. However, if a rectilinear magnifying optical instrument is panned over a flat motif, the image pixels pass in front of the eye in rapid succession and the visual barrel distortion becomes visible as an apparent convex curvature of the image.
In other words, it is a lens with little or no barrel or pincushion distortion. At particularly wide angles, however, the rectilinear perspective will cause objects to appear increasingly stretched and enlarged as they near the edge of the frame. These types of lenses are often used to create forced perspective effects.
The reverse, in which the perimeter is magnified more than the center, is known as "pincushion distortion" (figure 3b). This effect is called lens distortion or image distortion, and there are algorithms to correct it. Systems free of distortion are called orthoscopic (orthos, right, skopein to look) or rectilinear (straight lines). Figure 4
The general assumption that "undoctored" photos cannot distort a scene is incorrect. Perspective distortion is particularly noticeable in portraits taken with wide-angle lenses at short camera-to-subject distances. They generally give an unpleasant impression, making the nose appear too large with respect to the rest of the face, and distorting ...
Curvilinear barrel distortion Curvilinear pincushion distortion. Curvilinear perspective, also five-point perspective, is a graphical projection used to draw 3D objects on 2D surfaces, for which (straight) lines on the 3D object are projected to curves on the 2D surface that are typically not straight (hence the qualifier "curvilinear" [citation needed]).
For example, a greater degree of barrel and pincushion distortion is tolerated in lenses that span the focal length range from wide angle to telephoto with a focal ratio of 10× or more than would be acceptable in a fixed focal length lens or a zoom lens with a lower ratio. Although modern design methods have been continually reducing this ...
For example, I've seen a textbook explanation of how an aperture can cause barrel and pincushion distortion. —Ben FrantzDale 00:36, 13 November 2007 (UTC) [ reply ] The model provided for the lens distortion is very simplistic, and doesn't include any of the tangential/decentering distortion components, which are useful for subpixel accurate ...