A fisheye lens is a lens with a viewing angle close to or equal to 180° (maybe greater than 180°). It is an extreme wide-angle lens, fisheye lens is its common name. In order to maximize the viewing angle of the lens, the front lens of this photographic lens has a short diameter and a parabolic projection to the front of the lens, which is quite similar to the eyes of a fish, so it is called a fisheye lens.