Make wide-angle or fish-eye looking photos.
Distortion can be used to calibrate actual physical lens distortion or create artificial feelings of fish-eye or wide-angle looking photos. When straight lines are curved inwards in a shape of a barrel, this type of aberration is called barrel distortion. Pincushion distortion is the exact opposite of barrel distortion – straight lines are curved outwards from the center. This type of distortion is commonly seen on telephoto lenses, and it occurs due to image magnification increasing towards the edges of the frame from the optical axis.