LENSES

Lens Extenders

Lens extenders (also known as teleconverters) increase the effective focal length of your lenses. Find out how lens extenders can enhance your telephoto capabilities and prove helpful especially when you can't physically get closer to your subject.
Extenders, generally known as teleconverters, increase the effective focal length of lenses. Canon Extenders are available in two strengths, 1.4x and 2x. As the names suggest, the 1.4x Extender increases the focal length of your lens by a factor of 1.4, and the 2x by a factor of 2.

Canon EF Extenders are designed for use with a number of telephoto and zoom EF lenses. They do not work with EF-S or EF-M lenses. They can be used with a compatible EF lens on a Canon EOS R System camera with an EF-EOS R Mount Adapter. If you're using RF lenses, you need Canon RF Extenders, which are designed to work with certain RF lenses – more about these shortly.

Not all Canon lenses accept Canon Extenders. This is because of their construction – extenders have a protruding front element that will not fit into the rear of many EF lenses and some RF lenses. Compatible lenses have a recessed rear element, which creates space for the front element of the Extender. (In the case of the RF 100-500mm F4.5-7.1 L IS USM, you need to zoom to at least 300mm in order to move the rear optical elements enough to fit an RF Extender. It is not physically possible to use the Extender at the lower end of the lens's zoom range.)

Extenders are a relatively cheap and convenient way of enhancing your telephoto capability. But using them to increase focal length comes at a cost − reduced maximum aperture. The 1.4x Extender causes a decrease of one stop in the maximum aperture of the lens, while the 2x Extender causes a loss of two stops. This means you gain extra focal length at the expense of losing some light. If you attach a 1.4x Extender to an EF 70-200mm f/2.8L IS III USM lens, for example, it will become in effect a 98-280mm f/4 lens. If you use the same lens with a 2x Extender, it becomes a 140-400mm f/5.6 lens. In the same way, the EF 70-200mm f/4L IS II USM lens has a maximum aperture of f/4, but with a 1.4x Extender, the effective maximum aperture becomes f/5.6, while with a 2x Extender it becomes f/8.
Telephoto shot of an owl in a hollow in a tree standing amid long grass.

Using an Extender to increase the focal length of your lens can be very helpful when you are not able to move closer to your subject.

A closer telephoto shot of an owl in a hollow of a tree.

Adding an Extender, in this case a Canon Extender RF 2x to a Canon RF 600mm F11 IS STM lens, doubled the reach of the lens to 1,200mm.

Autofocus with Extenders

With the reduction of the maximum aperture, a side effect of this is that there is the possibility of the loss of autofocus when using an Extender with DSLR cameras. On many DSLR cameras, autofocus stops when the maximum effective aperture drops below f/5.6, regardless of the amount of light available. However, newer EOS cameras such as the EOS 77D, EOS 90D and EOS 7D Mark II and professional-level cameras such as the EOS 5D Mark IV and EOS-1D X Mark III allow autofocusing at maximum apertures of f/8.

All lenses in Canon's EF lens range have a maximum aperture of f/5.6 or wider, so all EF-mount cameras will autofocus with any autofocus lens. The f/8 autofocusing ability is needed only when you are using a lens and Extender combination that reduces the maximum aperture of the lens to f/8 or smaller. Some lens and Extender combinations mean that the maximum aperture of the lens is maintained at f/5.6 or wider and so autofocus remains unaffected.

The introduction of the EOS R System series, with the large RF lens mount, has shaken things up considerably. As mirrorless cameras, the EOS R System range use their full-frame imaging sensor for focusing. The EOS R and EOS RP feature Dual Pixel CMOS AF, while the EOS R5 and EOS R6 have Dual Pixel CMOS AF II. This means they have on-chip phase-detection focusing. Also, the EOS R System cameras can focus at f/22 and are not limited to f/5.6 or f/8 for autofocusing, as demonstrated by the introduction of the Canon RF 600mm F11 IS STM, RF 800mm F11 IS STM and RF 100-500mm F4.5-7.1 L IS USM lenses. In fact, they can even focus automatically when these lenses are mounted with the Canon Extender RF 1.4x or Extender RF 2x.
Close-up of a photographer's hand attaching a Canon Extender 1.4x II to a telephoto lens.

Fit a Canon Extender to a compatible lens, then attach the whole assembly to your camera, to increase the effective focal length of the lens.

Canon Extender RF 2x

If you're using an EOS R System camera and compatible RF lenses, you can extend your reach with an RF 1.4x Extender or RF 2x Extender designed specifically for the RF lens system, maintaining image quality and high speed communication between camera and lens.

Canon EF Extenders Mark III

In late 2010 Canon updated the EF Extender range to the Canon Extender EF 1.4x III and Canon Extender EF 2x III. These Extenders match the high image quality of the latest EF lenses and ensure the fastest and most accurate autofocus performance possible. Each Mark III Extender features an integrated microprocessor chip to provide complete communication between lens and camera and ensure that the focusing can be completed as quickly as possible.

Note that in order to ensure that the Extender-Lens combination is detected correctly, the Extender should be fitted to the lens first before attaching the whole combination to the camera.

The Canon EF Extenders Mark III are compatible with the following lenses, extending their focal lengths as below:

Lens

with EF 1.4x Extender

with EF 2x Extender

EF 135mm f/2L USM

189mm

270mm

EF 180mm f/3.5L Macro USM

252mm

360mm

EF 200mm f/2L IS USM

280mm

400mm

EF 200mm f/2.8L II USM

280mm

400mm

EF 300mm f/2.8L IS USM
EF 300mm f/2.8L IS II USM

420mm

600mm

EF 300mm f/4L IS USM

420mm

600mm

EF 400mm f/2.8L IS USM
EF 400mm f/2.8L IS II USM
EF 400mm f/2.8L IS III USM

560mm

800mm

EF 400mm f/4 DO IS USM
EF 400mm f/4 DO IS II USM

560mm

800mm

EF 400mm f/5.6L USM

560mm

800mm

EF 500mm f/4L IS USM
EF 500mm f/4L IS II USM

700mm

1,000mm

EF 600mm f/4L IS USM
EF 600mm f/4L IS II USM
EF 600mm f/4L IS III USM

840mm

1,200mm

EF 800mm f/5.6L IS USM

1,120mm

1,600mm

EF 1200mm f/5.6L USM

1,680mm

2,400mm

EF 70-200mm f/2.8L IS USM
EF 70-200mm f/2.8L IS II USM
EF 70-200mm f/2.8L IS III USM

98-280mm

140-400mm

EF 70-200mm f/2.8L USM

98-280mm

140-400mm

EF 70-200mm f/4L USM

98-280mm

140-400mm

EF 100-400mm f/4.5-5.6L IS USM
EF 100-400mm f/4.5-5.6L IS II USM

140-560mm

200-800mm

Canon RF Extenders

The Canon Extender RF 1.4x and Canon Extender RF 2x were announced in February 2020 for use with the EOS R System range of full-frame mirrorless cameras. As usual, using the Extender RF 1.4x incurs a 1-stop reduction in the maximum aperture and the Extender RF 2x brings a 2-stop reduction, but the lenses can still focus automatically. They are compatible with the following lenses, extending their focal lengths as below:

Lens

with RF 1.4x Extender

with RF 2x Extender

RF 600mm F11 IS STM

840mm

1,200mm

RF 800mm F11 IS STM

1,120mm

1,600mm

RF 100-500mm F4.5-7/1 L IS USM
(Extender usable only from 300mm focal length onwards)

420-700mm

600-1,000mm

Kirjoittaja Angela Nicholson


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