Canon Extender EF 2x III review: is twice as much twice as good?

The Canon Extender EF 2x III aims to double the focal length of compatible EF-mount Canon telephoto lenses with minimal drop in performance and image quality.

Canon Extender EF 2x III
(Image: © Matthew Richards)

Digital Camera World Verdict

I like that the Canon Extender EF 2x III doubles my telephoto reach but is only a tiny fraction of the size, weight, and cost of buying a whole extra super-telephoto lens. Build quality, handling and performance are all impressive.


  • +

    Twice the telephoto reach

  • +

    Built-in processor enhances performance

  • +

    Solid, weather-sealed build


  • -

    Drops 2 f/stops in aperture rating

  • -

    Slight degradation of image quality

  • -

    Incompatible with some lenses

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Surely the last in an illustrious line of Canon EF-mount 2x ‘extenders’ or teleconverters, the Mark III edition is designed for Canon cameras and compatible EF-mount Canon telephoto lenses. It’s primarily designed for DSLRs but can also be used on EOS R-system mirrorless cameras via an EF-EOS R mount adapter

As such, it’s one of the best teleconverters on the market. As a 2x teleconverter, the focal length of the attached lens doubled, with a reduction in aperture rating of two f/stops. For example, add it to a Canon EF 70-200mm f/2.8L IS III USM zoom and you effectively get a 140-400mm f/5.6 super-telephoto lens.

Swipe to scroll horizontally
MountCanon EF
Lens construction9 elements in 5 groups
Focal length multiplier2.0x that of main lens
Aperture reduction2 f/stops
Minimum focus distanceSame as main lens
Maximum magnification2.0x that of main lens
Filter sizeN/A
Dimensions72 x 52.7mm
Canon Extender EF 1.4x III

The Canon Extender EF 1.4x III gives 1.4x magnification rather than 2x, so it’s less powerful but smaller and lighter, and you only lose one f/stop in aperture rather than two stops.

Canon Extender RF 2x

If you use an EOS R-system camera, the Canon Extender RF 2x is the native equivalent for mirrorless camera bodies and compatible RF-mount telephoto lenses.

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Matthew Richards

Matthew Richards is a photographer and journalist who has spent years using and reviewing all manner of photo gear. He is Digital Camera World's principal lens reviewer – and has tested more primes and zooms than most people have had hot dinners! 

His expertise with equipment doesn’t end there, though. He is also an encyclopedia  when it comes to all manner of cameras, camera holsters and bags, flashguns, tripods and heads, printers, papers and inks, and just about anything imaging-related. 

In an earlier life he was a broadcast engineer at the BBC, as well as a former editor of PC Guide.