Even if the other possibleaberrations were totally eliminated, images could result that still have a distortedappearance. For an example, an rectangle may appear as a barrel or pin cushion-shapedobject. A lensaberration which does not affect the sharpness of the image, but alters the shapeof objects; the inability of a lens to render straight lines perfectly straight;does not improve by stopping down the lens; there are two types of distortion:Barrel:Straight linesare bowed in at the edges of the picture frame re sembling the sides of a barrel;pres ent in small amounts in some wideangle or wideangle-zoom lenses, bu~ uncorrectedin fisheye lenses.Pincushion: The opposite of barrel distortion;straight lines are bowed in toward the middle to resemble the sides of a pincushion;present in smal amounts in some telephoto and telephoto-zoom lenses.mirglossary
Misrepresentation of proportions of objects or of their arrangement in a scene. The two main types of lens distortion are: (1) Barrel distortion, in which the straight lines near the edges of the viewframe appear bowed outward from the center, like a barrel-shape; and (2) Pincushion distortion in which the same lines bend in towards the center. Another type is tonal distortion, in which an image s contrast, brightness or colors appear markedly different from those of the subject.
A defect in an image caused by the lens, such as barreling and pincushioning
Distortion is the variation of the magnification of the lens throughout the image field. In practical terms, photographic distortion describes the degree to which a lens cannot render straight lines in a scene as straight lines in the final image. Read more about how distortion is defined, measured and scored.
Variation from intended output -- usually undesirable -- caused by device characteristics.
There are three types of distortion that could affect the shape of the image: Barrel: image deformation causes a rectangle to swell in the center, looking like a barrel (the corners of the rectangle are greater than 90 degrees); Pincushion: image deformation causes the sides of a rectangle to move inward, forming a pincushion or star shape (the corners of the rectangle are less than 90 degrees); or Combinations: the two types can also be combined.Distortion cannot be corrected by stopping down the lens. It can be improved by the optical combination of positive and negative lens elements.