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 f/4L IS USM, they will multiply the focal length of the lens by a factor of either 1.4× or 2.0×. This will result in a focal length of 700mm or 1000mm, respectively, with a 500mm lens.
Canon has released six models:
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They are constructed with metal bayonets, and engineered plastic ends. There are no moving parts, other than the lens latch lock. Two generations of the extenders exist, the older 1.4× and 2×, plus the newer 1.4× II as well as 2× II. The newer II versions have weather-sealing and anti-reflective surfaces inside the extender body. The optical construction of the 1.4× versions are a of five-element design. Both 2× versions use seven elements, although the optical formula of the II version is different, to improve optical performance [1].
These Extender EF lenses can only be used with lenses that have a compatible mount. While all EF lenses have mount designs that can be used with EOS bodies, only lenses with accordant mounts can be used with the extender EF lenses. These lenses must have the clearance to accept the protruding lens on the extender, as well as 10 (3 extra) electronic contacts for proper electronic communication with the extender. These extra electronic contacts are used for sending the correct aperture information to the body. When a compatible lens is used with a 1.4× or 2× extender, it will cost the lens a one or two stop decline in aperture size, respectively. Autofocus speed of any used EF lens is also affected. When used with the 1.4× extender, autofocus speed is reduced to a half. When used with the 2× extender, autofocus speed is reduced to a quarter. Image stabilization may not work on lenses that are equipped with an extender, or on certain EOS bodies.
Though not specified by Canon as such, users have reported that the tilt-shift lenses in Canon's line-up can also be used with the extenders[3][4][5]. However, when used with an extender, the lens will not pass on the correct aperture to the camera. The focal length stored in the Exif data will also be incorrect.
The following is a list of EF lenses that are compatible with the Extender EF lenses together with their resulting focal lengths, and apertures. Also listed is the autofocus and image stabilization functionality.
| Lens | Lens with 1.4× | AF with 1.4× | IS with 1.4× | Lens with 2× | AF with 2× | IS with 2x |
|---|---|---|---|---|---|---|
| 135 mm f/2L USM | 190 mm f/2.8 | — | 270 mm f/4 | — | ||
| 180 mm f/3.5L Macro USM | 252 mm f/5[nb 1] | [nb 2] | — | 360 mm f/7.1[nb 1] | — | |
| 200 mm f/1.8L USM | 280 mm f/2.5[nb 1] | — | 400 mm f/3.5[nb 1] | — | ||
| 200 mm f/2.0L IS USM | 280 mm f/2.8 | 400 mm f/4 | ||||
| 200 mm f/2.8L II USM | 280 mm f/4 | — | 400 mm f/5.6 | — | ||
| 300 mm f/2.8L USM | 420 mm f/4 | — | 600 mm f/5.6 | — | ||
| 300 mm f/2.8L IS USM | 420 mm f/4 | 600 mm f/5.6 | ||||
| 300 mm f/4L USM | 420 mm f/5.6 | — | 600 mm f/8 | [nb 3] | — | |
| 300 mm f/4L IS USM | 420 mm f/5.6 | 600 mm f/8 | [nb 3] | |||
| 400 mm f/2.8L USM | 560 mm f/4 | — | 800 mm f/5.6 | — | ||
| 400 mm f/2.8L II USM | 560 mm f/4 | — | 800 mm f/5.6 | — | ||
| 400 mm f/2.8L IS USM | 560 mm f/4 | 800 mm f/5.6 | ||||
| 400 mm f/4 IS DO USM | 560 mm f/5.6 | 800 mm f/8 | [nb 3] | |||
| 400 mm f/5.6L USM | 560 mm f/8 | [nb 3] | — | 800 mm f/11 | — | |
| 500 mm f/4L IS USM | 700 mm f/5.6 | 1000 mm f/8 | [nb 3] | |||
| 500 mm f/4.5L USM | 700 mm f/6.3[nb 1] | [nb 3] | — | 1000 mm f/9.0[nb 1] | — | |
| 600 mm f/4L USM | 840 mm f/5.6 | — | 1200 mm f/8 | [nb 3] | — | |
| 600 mm f/4L IS USM | 840 mm f/5.6 | 1200 mm f/8 | [nb 3] | |||
| 800 mm f/5.6L IS USM | 1120 mm f/8 | [nb 3] | 1600 mm f/11 | |||
| 1200 mm f/5.6L USM | 1680 mm f/8 | [nb 3] | — | 2400 mm f/11 | — | |
| 70-200 mm f/2.8L IS USM | 98–280 mm f/4 | 140–400 mm f/5.6 | ||||
| 70-200 mm f/2.8L IS II USM | 98–280 mm f/4 | 140–400 mm f/5.6 | ||||
| 70-200 mm f/2.8L USM | 98–280 mm f/4 | [nb 3] | — | 140–400 mm f/5.6 | [nb 3] | — |
| 70-200 mm f/4L IS USM | 98–280 mm f/5.6 | 140–400 mm f/8 | [nb 3] | |||
| 70-200 mm f/4L USM | 98–280 mm f/5.6 | — | 140–400 mm f/8 | [nb 3] | — | |
| 100-400 mm f/4.5-5.6L IS USM | 140–560 mm f/6.3-8[nb 1] | [nb 3] | 200–800 mm f/9-11[nb 1] | |||
| TS-E 17 mm f/4L | 24 mm f/5.6 | [nb 4] | — | 34 mm f/8 | [nb 4] | — |
| TS-E 24 mm f/3.5L | 35 mm f/5.0[nb 1] | [nb 4] | — | 50 mm f/7.1[nb 1] | [nb 4] | — |
| TS-E 45 mm f/2.8 | 65 mm f/4.0 | [nb 4] | — | 90 mm f/5.6 | [nb 4] | — |
| TS-E 90 mm f/2.8 | 125 mm f/4.0 | [nb 4] | — | 180 mm f/5.6 | [nb 4] | — |
| Key | ||||||
| Autofocus: | - AF works. - AF works only with EOS bodies that can AF at f/8. - AF does not work. | |||||
| Image stabilization: | - IS works. - IS works only with supported EOS bodies (generally, bodies introduced since approximately 1995). | |||||
Canon EOS bodies that have a high density, high precision auto-focus sensor with 45 AF points are able to autofocus at maximum apertures of f/8.[10]
Although the upcoming Canon EOS-1D X, the replacement for both the 1D Mark IV and 1Ds Mark III, will have 61 AF points, it will not autofocus with any lenses or lens/extender combinations whose maximum aperture is smaller than f/5.6.[11]
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