It’s fair to say that we have all been in a situation where we would like extra zoom or reach from our chosen lenses. Buying a longer lens is an option, but if you don’t have the budget for another high-quality lens, Canon EF lens extenders come into play. Also referred to as teleconverters, lens extenders essentially bolt on to the back of a lens and multiply the focal length from 1.4 times to two times its current values.
A 1.4x lens extender can provide 40 percent extra range, while a 2x converter doubles your current focal length. Additional plus points include weight saving, i.e. not having to carry around the extra heft of another telephoto lens, and you still have the original focal reach of your lens for more close-up work.
This all sounds wonderful, but these added attachments also have a bunch of caveats. As the physical length of a lens increases when using a lens extender, other aspects of the lens also change. Firstly, the aperture of a lens will become essentially smaller.
When a 1.4x extender is used, the aperture will drop by one stop. When using a 2x extender, the lens will experience a two-stop drop in light-gathering abilities. For instance, an f/4 aperture lens will result in an f/5.6 aperture or f/2.8-f/4 with the 1.4x version, thus needing more external light for an image.
When the aperture size drops, shutter speeds slow down, which means it’s harder to shoot in low light conditions. Then there is the issue of autofocusing, with some lower-priced cameras needing manual focus only.
When the focal length is increased, a lens is more susceptible to camera shake, so you had better use a tripod or make the most of image stabilization.
A lens extender will also multiply any anomalies associated with a lens. This is why the best quality lenses should be used with an extender. One last point is that they will only work with certain types of lenses.
These caveats mean that you shouldn’t use an extender with every shot and a stopped down aperture is always a must. In the right circumstances, a lens extender can be an extremely useful piece of kit.
As you are now aware of the positives and negatives of these contraptions, let’s have a closer look at the best quality Canon EF lens extenders on the market and what they can provide.
1. Canon Extender EF 1.4x III (Overall Winner)
The Canon Extender EF 1.4x III is a commonly used unit for the Canon EF mount, extending the focal length by a 1.4x factor. Canon’s own offering in this department ensures the best quality glass, along with the best communication between lens and camera.
The third iteration of this extender brings an upgraded optical design, better weatherproofing, and quicker communication. Just like a high-quality lens, the EF 1.4x III features seven optical elements in three groups, each having a Super Spectra coating, plus a Fluorine coating on the front and rear elements.
The extender also features an integrated processor to handle all the complicated matters of autofocusing and metering. Plus, the unit is fully weather-resistant to handle most environmental conditions.
As previously mentioned, the 1.4x extender reduces the maximum aperture by one stop, which is not always a problem on an f/2.8 zoom but starts to feel a little detrimental on an f/4 lens, with the aperture now being f/5.6. However, with an L-series lens that has been stopped down a little, the extender produces wonderfully sharp images and with the extended range, excellent bokeh effects.
The overall image quality cannot be faulted considering all the optical and technical wizardry going on behind the scenes, with the only detriment being when the aperture is fully stopped down. This unit is expensive and will only work with compatible L-series lenses, but if you want to extend the range of your lens without selling a family member for a new zoom, the EF 1.4x III is a great choice.
Just like the EF 1.4x III above, the Canon Extender EF 2x III contains high-quality glass and is one of the best extenders for the Canon platform. In this case, increasing the focal length of the lens by a factor of 2x or essentially doubling its reach.
This particular version features nine elements arranged in five groups with a Super Spectra Coating and a Fluorine Coating on the front and rear elements. The EF 2x III also features an integrated processor to handle all information transfers and comes with full weatherproofing.
Just like its sibling above, a simple release mechanism makes it quick and easy to attach to lens and camera, with a solid fit that’s just as secure as a regular lens to body attachment. The extender drops the overall aperture by two stops, which essentially means a lens with a maximum aperture of f/2.8 becomes f/5.6, and an f/4 lens results in an f/8 aperture.
Compatibility wise, the EF 2x III works with L-series lenses 135mm and beyond, but you will have to check the full list of acceptable lenses on the Canon website or official sources.
Although you will need plenty of light when using this extender due to the reduced aperture and shutter speeds, images generally come out clean and detailed. This point will largely depend on the particular camera and lens being used, but the general course of action is to use a wide aperture setting for the sharpest results.
There is no faulting the communication between lens and camera body, with autofocusing working as expected. The latest version of this extender is the one to go for as it will produce the sharpest results and the quickest communication.
Although the Kenko TELEPLUS HD 1.4X DGX is actually cheaper than the Sigma below, the Sigma is the best version for Sigma lenses and has slightly better optics. This extender can increase the range of Canon EF/EF-S telephoto lenses with a 1.4x increased focal length.
The optics are arranged with three elements in two groups, plus a multi-coating and electronic contacts for full communication with the camera body. Like the other extenders on this list, the aperture drops by 1EV but also increases the likes of a 70-200mm lens to a 98-280mm lens.
We found that the image quality is very good when using this extender, but its full workings can depend on the particular camera body and lens being used. Therefore, it’s imperative with this extender to try it out in person with your own particular camera body and lenses.
4. Sigma APO TELE CONVERTER 1.4x EX DG (Budget Winner)
The Sigma APO TELE CONVERTER 1.4x EX DG is essentially for strapping high-quality Sigma lenses to a Canon EF mount. For the full list of compatible lenses, check out the Sigma website here.
This extender will increase the focal length by 40% or 1.4x, while also decreasing the aperture by one stop. Full communication between lens and camera is maintained, with full use of autofocusing and metering in-camera. This converter may not have some of the fancy optics as found in the Canon versions, but it does have a multi-layer coating for reducing the likes of lens flare and ghosting.
When this converter is used on longer lenses, you will need a tripod as mandatory or an extremely steady hand. On the likes of the Sigma 70-200mm f/2.8 DG OS HSM Sports the aperture was reduced to f/4, but also produced a total reach of 448mm.
The sharpest results from the Sigma came out at f/5.6, as f/4 produced ever so slight softening in the copy we had at hand. Therefore, if you have a compatible camera body and lens to go with this extender, it’s a good value option for Sigma lenses.
Summing up the Best Canon EF Lens Extenders
Lens converters or extenders are quite specialist and niche products. But, when you need an extra reach of focal length and you have no other lens at hand, they can be a real lifesaver.
They may also seem initially expensive, but considering that the optics have to be as good as a lens, with seamless communication, they do a lot for the asking price. For Canon lenses, the obvious choices are the top two offerings above, but for a budget option, the Kenko is still very respectable.