Barrel distortion

Barrel distortion is most often seen in convex mirrors.

The image is enlarged in the center and compressed at the edges. Parallel lines are distorted like the spaces between the staves of a wooden barrel. Convex mirrors have the advantage of creating a very wide field of view. They are used as insets in rear-view mirrors, to deter shoplifters in supermarkets, and are mounted at blind corners to assist motorists. The reflections shown above are in a ceiling mirror (left), and a convex supermarket mirror placed on the ground (right).

Images with slight barrel distortion can be corrected with the Spherize function in PhotoShop.

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