The Canon EF 600mm is a super-telephoto 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...

 made by Canon Inc.

Canon Inc.

is a Japanese multinational corporation that specialises in the manufacture of imaging and optical products, including cameras, camcorders, photocopiers, steppers and computer printers. Its headquarters are located in Ōta, Tokyo, Japan.-Origins:...

 The lens has an EF

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...

 mount to work with the EOS

Canon EOS

The Canon EOS autofocus 35 mm film and digital SLR camera system was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current DSLR system...

 line of cameras.
4L USM lens was released in November 1988 (923,000 yen) 4L IS USM lens was released in September 1999 (1,290,000 yen)4L IS II USM lens was announced in February 2011

The IS version has more lens groups and elements, and the weight was reduced from 6kg to 5.36kg. Both lenses are compatible with the Canon Extender EF

Canon Extender EF

The Extender EF lenses are a group of teleconverter lenses made by Canon. These lenses are used between any compatible EF type lens and any of the Canon EOS line of cameras. When used with a compatible lens, such as the Canon EF 500mm 4L IS USM, they will multiply the focal length of the lens by a...

teleconverters.