The Canon EF 400mm are four super-telephoto lenses 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:...

 These lenses have an EF mount that 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. These lenses are widely used by sports

Sports photography

Sports photography refers to the genre of photography that covers all types of sports.In the majority of cases, professional sports photography is a branch of photojournalism, while amateur sports photography, such as photos of children playing association football, is a branch of vernacular...

 and wildlife photographers.

Canon currently manufactures four 400mm prime lens

Prime lens

In film and photography, a prime lens is either a photographic lens whose focal length is fixed, as opposed to a zoom lens, or it is the primary lens in a combination lens system....

es:

• EF 400mm 2.8L IS USM
• EF 400mm 2.8L IS II USM
• EF 400mm 4 DO IS USM
• EF 400mm 5.6L USM

The EF 400mm 5.6L USM is Canon's least expensive 400mm lens. Having a maximum aperture of 5.6, it is relatively slow

Lens speed

Lens speed refers to the maximum aperture diameter, or minimum f-number, of a photographic lens. A lens with a larger maximum aperture is a fast lens because it delivers more light intensity to the focal plane, allowing a faster shutter speed...

.

The 400mm 4 DO IS USM is one of only two Canon lenses that make use of diffractive optics

Diffraction

Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665...

 (the other is the Canon EF 70-300mm lens

Canon EF 70-300mm lens

The EF 70-300mm lens is a telephoto zoom lens made by Canon Inc.The lens has an EF mount to work with the EOS line of cameras.Three Canon EF telephoto zoom lenses carry the 70-300mm designation. These are the EF 70-300mm 4.5-5.6 DO IS USM, EF 70-300mm 4-5.6L IS USM and the EF 70-300mm 4-5.6 IS USM...

). The use of diffractive optics allows the lens to be significantly lighter than it might otherwise be, but at the cost of some image quality.

These 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.