Lens distortion is most pronounced at the edges of the image and the amount of distortion can vary with focal length in telephoto or zoom lenses, usually more pronounced at the wide angle end in such cases. This product of this ocular distortion is the result of a spherical lens projecting an image onto a flat image sensor or film frame. All lenses exhibit this effect to some degree with the amount shown here a fairly typical example. The result is a noticeable bending of lines known to be otherwise straight regardless of direction but most recognizable in the vertical or horizontal plane.