Watch this video from Niall Hampton, Editor of Digital Camera magazine, on 5eleconverters and the 5 things you need to know about them.
A teleconverter or extender is a gadget that fits between the lens and the camera body to magnify the image made by the lens. A teleconverter sounds like the ideal solution for getting closer to a subject with your lens.
In practice, though, teleconverters have disadvantages, including the effect they have on your lens’s maximum aperture and often on the overall optical quality of your photos.
And you need to choose wisely, as teleconverters will not work well with all lenses and cameras. At one time, they were sold as inexpensive gadgets that were widely compatible with different camera systems and lenses, but these days lens and camera designs are more complex, with sophisticated electronic data transfer and, sometimes with protruding rear lens elements. There are few 'generic' teleconverters still on the market and these have to be chosen with care to match your lenses.
But teleconverters have not disappeared. They have taken on a new role, mostly in long-range sports and wildlife photography. A high-quality ‘dedicated’ teleconverter can massively increase the reach of a telephoto lens and saves the expense and weight of carrying bigger, longer telephotos.
But what do you need to know when choosing a teleconverter for your DSLR or mirrorless camera system?
1) Teleconverter magnification
Teleconverters come in three strength settings. 1.4x is the most common: it gives a useful increase in magnification without a big penalty in usability or image quality. They increase the focal length of the lens it is used with, so a 300mm becomes a 420mm – and a 70-200mm becomes a 98-280mm zoom
2x converters (also known as doublers) are popular too because they double the focal length, although the image quality may not be as good.
Some makers, such as Nikon, produce intermediate 1.7x teleconverters.
2) Teleconverters and maximum aperture
Because the lens’s image is being enlarged, the effective lens aperture is decreased. A 1.4x teleconverter brings a one-stop reduction in maximum aperture; a 2x teleconverter brings a two-stop reduction.
So if you use a 1.4x converter on a 300mm f/4 it becomes a 420mm f/5.6. And if you use a 2x teleconverter on a 70-200mm f/2.8 it becomes a 140-400mm f/5.6.
This means that teleconverters work best with lenses that have a wide maximum aperture to start with. You may need to accept either slower shutter speeds or higher ISO settings, and you won’t be able to reproduce the shallow depth of field effects you normally get with that lens.
3) Teleconverters and autofocus compatibility
This reduction in maximum aperture could affect your camera’s autofocus system, since many won’t work with apertures lower than f/8; you may have to resort to manual focus.
You should also make sure that your lens’s aperture control and any image stabilisation will still work as normal (you won’t have a problem with teleconverters manufactured by the maker of your lens) and that the lens will still supply correct EXIF (shooting) information to the camera.
4) Teleconverter compatibility
Obviously you need to make sure that any teleconverter you buy will fit your camera body and your own lenses, especially since some teleconverters or lenses have protruding elements.
This won’t be such an issue when you’re buying makers’ own dedicated teleconverters, but it’s definitely worth checking if you buy a cheap and relatively unknown generic brand online.
5) Teleconverters and optical quality
Apart from the loss in maximum aperture, the biggest drawback of teleconverters is a potential loss in image quality. This is because you’re effectively magnifying the central part of the image captured by the lens, along with any defects or aberrations.
Dedicated ‘matched’ teleconverters will be designed to optically complement the lens they’re attached to, but cheaper generic teleconverters won’t be.
6) Own-brand teleconverters
Most camera and lens makers offer teleconverters for use with a small selection of their own telephoto or super-telephoto lenses. The teleconverter’s optical layout will be optimised for those lenses. Autofocus, image stabilisation and exposure controls will work as expected too. Canon, Nikon, Olympus, Panasonic, Fujifilm and other camera manufacturers make teleconverters with their cameras and lenses. Lens manufacuturers, notably Sigma, make teleconverters to work with Sigma lenses on a number of different camera body mounts.
7) Dedicated teleconverters
Dedicated, or matched, teleconverters are custom-designed for one specific lens, and offer a good solution for photographers who don’t want to compromise own quality but do need to travel light.
8) Generic third-party teleconverters
Third party teleconverters, such as those made by Kenko, are designed to offer a low-cost option. These are available in a number of different mounts - the mount for the lens it is used with is almost always the same as the camera mount the pair are being fitted onto. You need to check compatibility with your camera and lens carefully before buying.
Teleconverters for Canon
Canon Extender EF 1.4x III
Optimised to match Canon’s professional DSLR telephoto lens range, this 1.4x converter offers dust and water resistance, Canon’s own Spectra coating and integrated processor for electronic communication. A protruding front element on the teleconverter means that this can not be used on all Canon EF lenses – so check compatibility.
Canon Extender EF 2x III
The 2x version of Canon's extender - again designed to work with just a few of its professional EF telephoto lenses. Check compatibility with your lens and camera before you buy.
Kenko Teleplus 1.4x HD Pro Teleconverter - Canon fit
Recently updated to new HD Pro specifications, the Kenko teleconverter is available in Canon EF (not EF-S compatible) mount. This 1.4x version is a good all-round choice – but do check compatibility with the DSLR and the lens you want to use this with.
Teleconverters for Nikon
Nikon TC-14E AF-S Teleconverter III
This is the 1.4x teleconverter for Nikon's range of DSLRs (and with the Z series of mirrorless cameras, if used with the FTZ adaptor). It is designed to work with a range of telephoto prime lenses from Nikon's vast family of Nikkor optics... check compatibility with your lens before you buy.
Nikon TC-20E AF-S Teleconverter III
This is the 2x teleconverter for Nikon's range of DSLRs. It is designed to work with a range of telephoto prime lenses from Nikon's vast family of Nikkor optics... check compatibility with your lens before you buy. It can be used with the Nikon Z6 and Nikon Z7 if used in conjunction with the FTZ adaptor.
Kenko Teleplus 1.4x HD Pro Teleconverter - Nikon fit
Recently updated to new HD Pro specifications, the Kenko teleconverter is available the F-mount used on Nikon DSLRs. This 1.4x version is a good all-round choice – but do check compatibility.
Teleconverter for Sony cameras
Sony 1.4x SEL14TC Teleconverter - E mount
This 1.4x converter is compatible with Sony's E-mount range of mirrorless cameras and the following three of its own telephoto lenses:
FE 70-200mm f/2.8 GM OSS,
FE 100-400mm f/4.5-5.6 GM OSS , and the
FE 400mm f/2.8 GM OSS.
Teleconverter for Fujifilm cameras
Fujinon Teleconverter XF2X TC WR
This 2x teleconverter is designed to work with Fujifilm's X series of mirrorless cameras, and is specifically matched to three key Fujifilm telephoto lenses: XF80mmF2.8 R LM OIS WR Macro,
XF50-140mmF2.8 R LM OIS WR and
XF100-400mmF4.5-5.6 R LM OIS WR.