The Sigma 10m f/2.8 EX DC fisheye is a photographic lens

Photographic lens

A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...

 manufactured by Sigma Corporation

Sigma Corporation

is a Japanese company founded in 1961, manufacturing cameras, lenses, flashes and other photographic accessories. All Sigma products are produced in the company's own Aizu factory in Bandai, Fukushima, Japan...

. It is a diagonal fisheye lens

Fisheye lens

In photography, a fisheye lens is a wide-angle lens that takes in a broad, panoramic and hemispherical image. Originally developed for use in meteorology to study cloud formation and called "whole-sky lenses", fisheye lenses quickly became popular in general photography for their unique, distorted...

. Unlike most fisheye lenses, this lens is designed for digital SLR cameras

Digital single-lens reflex camera

Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....

 that do not have a full 36x24mm sensor. This results in a much greater fisheye effect than is possible when a full-frame fisheye lens is used with a smaller sensor.

This lens is available in Canon

Canon EF lens mount

Introduced in 1987, the EF lens mount is the standard lens mount on the Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens...

, Nikon

Nikon F-mount

The Nikon F-mount is a type of interchangeable lens mount developed by Nikon for its 35 mm SLR cameras. The F-mount was first introduced on the Nikon F camera in 1959, and features a three lug bayonet mount with a 44 mm throat and a flange to focal plane distance of 46.5 mm...

, and Sigma

Sigma SA mount

The Sigma SA mount is a design of lens mount designed by the Sigma Corporation of Japan for use on their single-lens reflex camera designs. The SA mount uses a bayonet mount which is physically similar to the Pentax K mount but uses a flange focal distance of 44 mm, identical to that of the Canon...

, Pentax

Pentax K mount

The Pentax K mount, sometimes referred to as the "PK mount", is a lens mount standard for mounting interchangeable photographic lenses to 35 mm single-lens reflex cameras. It was created by Pentax in 1975, and has been used by all Pentax 35 mm and digital SLRs since...

, and Sony mounts.