Barrel Distortion is a effect commonly found in low end wide angle lenses, and wide angle converters in which the lens does not compensate for the larger angle of view properly, and can cause straight lines to have a bow to them in the final image. This effect can be seen with most ‘kit’ lenses included with SLR cameras. To produce the effect, take a photo at your camera’s widest angle close up to something with straight lines, such as a building or a window frame.

This effect can be greatly reduced utilizing Photoshop’s Filter ‘Lens Correction’ under the distort menu.

See also: pincushion distortion