Changing the character of lenses with Canon EF Extenders: Part I

December 03, 2013

Canon’s EF tele extenders have been available to EOS shooters since the early days of the EOS system, the late1980s. Now in their third generation, the EF 1.4x III and EF 2x III Extenders are popular accessories with many professionals and advanced amateur shooters. With the recently-announced firmware updates for Canon’s EOS-1D X and EOS 5D Mark III cameras, which will permit AF with a lens/extender combination as slow as f/8, you may be reconsidering adding EF Extenders to your camera bag for certain shooting situations. We’ll explore the technical aspects of Canon’s EF Extenders in a separate article here on the Canon Digital Learning Center. But initially, we want open the door to some of the possibilities that extenders can provide the serious enthusiast or working professional.

One huge thing is how one or both EF Extenders can transform what a lens can do in many situations and that’s what we’ll primarily explore in this article. While some users consider an extender to be an accessory that they’ll add on rare occasions, there are others who regard their lens and extender combination to be almost standard equipment, and who remove the extender primarily to convert the lens into a faster, shorter focal length telephoto when that’s what’s needed.

A quick review of tele extender basics

This is strictly a review of basics for most readers, but still important for everyone:

  • Tele extenders cause an unavoidable loss in light transmission to the imaging sensor or film. There’s a constant, steady 1-stop light loss with 1.4x Extenders and a 2-stop loss with a 2x. This is consistent, regardless of camera or lens brand.
  • A 1.4x Extender multiplies the effective lens focal length by 1.4x. Thus, a 300mm lens would have the power and field of view of a 420mm lens. And a 2x Extender doubles the effective lens focal length.
  • When using a digital SLR with an image sensor smaller than a full-frame, it’s “crop factor” is added to whatever an extender is to calculate effective lens coverage relative to a full-frame camera. In other words: an EOS Rebel has a 1.6x crop factor. If using a 200mm lens with a 2x Extender (400mm equivalent), putting it on an EOS Rebel would result in a lens that effectively “acts” like a 640mm lens (400mm x 1.6 = 640mm) would on a full-frame or 35mm film camera.
  • Tele extenders do not impact or change a lens’ minimum focus distance. Because extenders do impact effective focal length, at minimum focus distance, a lens with extender provides a noticeably tighter composition of small objects than the lens alone would.
  • Canon EF 1.4x and 2x Extenders are exclusively designed to work with specific, compatible Canon EF lenses. Part of the reason for this is the front element design of Canon extenders, which literally projects forward and into the rear of any lens they’re attached to. This enhances optical performance with those lenses, but prevents their attachment to many lenses that have a rear element flush with the rear lens mount.
  • Canon EF lenses that are extender-compatible:
    • All fixed focal length EF L-series telephoto lenses, 135mm and above (thru 800mm)
    • All white-colored EF 70-200mm f/2.8 and f/4 L-series zoom lenses (all versions)
    • EF 100–400mm f/4.5–5.6L IS USM zoom
    • EF 200–400mm f/4L IS USM Extender 1.4x zoom (can be used in addition to lens’ built-in 1.4x)
Canon EF Extenders and super-telephoto lenses

This is the place many EOS shooters think of applying extenders, and it’s obvious why: the ability to take an already powerful lens, like an EF 500mm f/4L IS II USM or EF 600mm f/4L IS II USM, and further expand on its telephoto power for relatively modest costs and practically no increase in size or weight has obvious appeal to wildlife, nature and some sports shooters. All of Canon’s fixed focal length super-tele lenses, from 300mm upward, are compatible with all versions of the 1.4x and 2x tele Extenders. And considering their modest cost, an EF 1.4x or possibly a 2x Extender is often an easy buying decision for shooters investing in super-tele lenses.

But for many users, the hidden practicality of the extenders is what happens when they’re combined with less obvious Canon EF lenses.

Extenders and everyday lenses — The EF 135mm f/2.0L IS USM

This is one of Canon’s sharpest mid-range tele lenses and one that’s carved out a spectacular reputation for available-light candid shooting. But what many users don’t immediately think of is that this is the shortest fixed focal length EF lens that’s officially compatible with EF Extenders. With a full-frame camera, any version of Canon’s EF 1.4x Extender produces an effective 189mm f/2.8 lens — virtually a 200mm f/2.8 and close to the classic 180mm focal length that commercial and fashion shooters relied on for decades during the film era.

Now, stop for a moment and consider this lens on an EOS body with a smaller APS-C size sensor, like an EOS 60D or 7D. Effectively adding the 1.4x Extender on those cameras, along with the camera’s 1.6x “crop factor,” produces a tack-sharp, compact and light 302mm f/2.8. It’s virtually the same field of view as an EF 300mm f/2.8L IS II USM on a full-frame camera, at a tiny fraction of the size, weight and cost of that lens and a full-frame body. This would be a terrific package to consider for indoor sports — hockey, basketball, ice skating, swimming and so on. Again, removing the extender brings you back to an f/2.0 lens for shooting in even more dimly-lit conditions.

The Canon EF 2x Extender can be used as well, resulting in a 270mm f/4 lens on a full-frame camera and the equivalent of a super-telephoto 432mm f/4 lens if it’s used on an APS-C size sensor camera with the 1.6x “crop factor.” Once again, for far less than the price of a super-telephoto lens, this combination could produce super-tele type magnification along with an aperture bright enough to be used in many indoor or low-light situations.

These are the types of combinations that may not instantly occur to some photographers when considering a tele extender. But an investment in a fixed focal length lens like the 135mm f/2.0L, along with one or both of the extenders, can really expand the imaging capabilities of a user’s system. And, this type of combination is doubly effective in situations when a lens’ size, weight, bulk and/or conspicuousness are factors.

The EF 200mm f/2.8L II USM

What’s been said about the EF 135mm f/2.0L and extenders applies likewise to the extremely underrated EF 200mm f/2.8L II USM lens. Virtually half the weight of the popular EF 70-200mm f/2.8L IS II USM lens, and with excellent inherent sharpness along with fast AF, the EF 200mm f/2.8L II USM lens is a very interesting alternative and an excellent candidate to combine with tele extenders.

With a 1.4x Extender mounted on a full-frame EOS camera, the lens converts into a 280mm f/4 lens and the equivalent of an extremely compact 400mm f/5.6 when used with the 2x Extender. Sharpness remains excellent with either extender and the lens with both of Canon’s EF Extenders would cost less than the EF 70-200mm f/2.8L IS II USM zoom lens. This is a factor to consider if the 200mm ceiling of the EF 70-200mm f/2.8L IS II USM zoom lens seems insufficient for whatever reason. And, of course, the lens can be “converted” into a premium-quality f/2.8 lens at 200mm by removing the extender.

These shorter-than-super tele lenses, combined with EF Extenders, become especially interesting when combined with small-sensor digital SLRs, from the EOS Rebel series up to the EOS 7D. That same EF 200mm f/2.8L II USM lens, combined with a 1.4x Extender, now provides an effective 448mm f/4 lens – getting close to 500mm f/4 territory, in terms of lens coverage, but at a far less size, weight and cost versus a fixed focal length EF 500mm f/4L IS II USM lens. Minimum focus remains at 4.9 feet, significantly less than a 400mm or 500mm super-tele lens would generate without extension tubes (not the same thing as a tele extender!). The EF 200mm f/2.8L II USM, used in this way, is transformed into an effective lens for many sports applications, from outdoor to indoor sports at well-lit facilities, where longer focal lengths are often a prerequisite for professional-level, tight compositions.

The EF 200mm f/2.0L IS USM

The size, weight and cost of this lens — along with its absolutely stunning image quality when combined with extenders — separate this lens from almost any other Canon EF lens on the market. Simply put: tele extenders transform this lens, turning it from one of the industry’s finest available-light lenses into an optical Swiss Army knife that can handle outdoor sports and even situations like night football on adequately-lit fields. Certainly, an investment in this lens plus extender(s) is substantially more than either the EF 135mm f/2L USM or EF 200mm f/2.8L II USM. But the character of this lens and how extenders contribute to its possibilities make it a force that serious shooters, in particular working professionals, should strongly consider.

First and foremost, optical performance for any lens with an extender is largely dictated by the lens itself. The fewer aberrations in the lens, the fewer anomalies you’ll see when looking closely at shots taken when it’s combined with a tele extender. This is one of the strongest performing EF telephoto lenses, superb in its contrast, sharpness, color rendition and ability to produce fine detail on high-resolution digital SLRs. Simply remove the extender and you’ve got a lens for available-light candids, indoor sports, theater work and so on.

Professional sports shooters have found that from courtside shooting locations, the EF 200mm f/2.0L IS USM lens is perfect for tight vertical shots, such as a professional tennis player, with a full-frame camera. Indeed, the EF 200mm f/2.0L IS USM is a commonly seen lens on the professional tennis circuit — even in bright outdoor conditions.

Add any version of the EF 1.4x Extender with a full-frame camera and the lens now “acts” like a superb-quality 280mm f/2.8 lens — still fast enough for low-light applications like theater work, basketball or even wedding candids when the photographer is forced to work at a distance from the altar at a church service. Image quality barely takes a hit, compared to using the lens alone. It cannot be overstated: the EF 200mm f/2.0L IS USM lens with a 1.4x Extender is a compelling professional alternative to the EF 300mm f/2.8L IS II USM lens for shooters who will be doing work involving available-light, whether it’s photojournalism or even fashion shoots on-location.

And when combined with a 2x Extender — especially the latest EF 2x III, which offers the best image quality yet in a Canon 2x tele extender — the lens now becomes long enough for outdoor sports and even some nature-type applications. With a full-frame camera, the 2x Extender makes the EF 200mm f/2.0L IS USM “act” like an EF 400mm f/4 DO IS USM lens, with excellent L-series image quality and Image Stabilization that makes hand-holding (or monopod shooting) eminently practical.

Now, again, consider the prospects if the EF 200mm f/2.0L IS USM is used with the 2x Extender and mounted on an EOS 7D or similar small-sensor camera. The 1.6x “crop factor” generates an effective field of view equivalent to 640mm, without any loss of the f/4 maximum aperture. It’s a truly hand-held 640mm f/4 lens with Image Stabilization that can be converted into a f/2 lens any time added lens speed is needed in dimly-lit conditions. Without an extender mounted, the EF 200mm f/2.0L IS USM is equivalent to a 320mm f/2 lens on a camera with APS-C size imaging sensor.

Perhaps more than any other lens in the Canon system, tele extenders change the whole character of this outstanding professional lens. Furthermore, the possibilities offered by the EF 1.4x and/or EF 2x Extenders may mean that for the working professional or very serious EOS enthusiast, this one lens may take the place of two or more high-end tele lenses.

The EF 70-200mm f/4L IS USM

The possibilities of the fixed focal length EF 135mm f/2.0L USM and EF 200mm f/2.8L II USM lenses, described above, speak strongly to their image creating potential for serious and critical EOS shooters. But there’s no doubting the flexibility of zooms and one of the world’s finest medium-telephoto zooms is the Canon EF 70–200mm f/4L IS USM.

This compact and lightweight lens — about half the weight of the f/2.8 L-series 70–200mm zoom and virtually the same as the EF 200mm f/2.8L II USM — is a great place to add tele extenders. Because its maximum aperture is a slower f/4, the 1.4x Extender is the first one most shooters would consider. An important point (we’ll discuss this in a separate article about the technical matters of tele extenders) is that with most EOS cameras, you have full AF as long as the lens (or lens + extender combination) has an effective maximum aperture of f/5.6 or faster. With its one-stop light loss, the 1.4x Extender combined with the EF 70–200mm f/4L IS USM falls within this window.

With a full-frame camera, many users find that 200mm is effectively a line of demarcation in telephoto coverage. At 200mm and under, many users find lenses like those in the EF 70–200mm f/4L IS USM category to be great for photographing people and other subjects in controlled situations. For more candid shots, whether of people or wildlife, it’s often practical to move back more than is comfortable with a EF 200mm f/2.8L II USM. Enter the EF 1.4x III Extender. With a full-frame camera, you now have the equivalent of a 98–280mm zoom — very similar in optical character to an EF 70–300mm f/4-5.6L IS USM lens. And once again, that combination on a small-sensor digital SLR, from the Rebel series up to the EOS 7D, would result in an effective 157–448mm f/5.6 lens. At a fraction of the weight of the EF 100-400mm f/4.5-5.6L IS USM lens on a full-frame camera, you’d have the same basic imaging potential.

One thing this lens with extenders highlights is the practicality of Image Stabilization. As extenders magnify effective focal length, they also magnify camera shake and the steadying effect of Image Stabilization is even easier to see in the viewfinder when an extender is mounted on a lens, and there’s no doubt that use of Image Stabilization with extenders is a big step in the direction for sharper images. That said, the less-expensive EF 70-200mm f/4L USM version of this lens (which doesn't have Image Stabilization) works beautifully with extenders. Finally, even though with most EOS bodies you’ll lose AF if the 2x Extender is used, this can be an effective combination for longer-range shooting with either version of the EF 70–200mm f/4L lens.

The EF 70–200mm f/2.8L IS USM

Here is one of the most popular Canon EF lenses among professional shooters and it’s one that is frequently considered for use with tele extenders. An important benefit of the f/2.8 design is that even with the 2x Extender, which causes a 2-stop light loss, you’re still at an effective maximum aperture of f/5.6 — so AF is possible with the 2x Extender in place on any Canon EOS SLR manufactured to date.

Any version of Canon’s EF 70–200mm f/2.8 L-series lenses, with or without Image Stabilization, is officially compatible with Canon-brand tele extenders. As mentioned above, Image Stabilization becomes a hugely valuable asset when a lens and extender are hand-held, particularly when using the 2x Extender. But the extenders certainly can be used on non-Image Stabilization versions of this lens as well.

The 2x Extender is an interesting place to start. On a full-frame camera, it results in an effective 140–400mm f/5.6 lens that can be easily hand-held and is excellent for many outdoor situations, even for sports. Once again, if a camera with the smaller APS-C size imaging sensor is used (such as an EOS 7D, 70D and so on), the 1.6x “crop factor” now multiplies the effective field of view into the equivalent of what a 224–640mm f/5.6 lens would provide on a full-frame camera — now firmly into super-telephoto territory.

For shooters who primarily work close to their subjects and only occasionally need long-range coverage, any version of the EF 2x Extender fundamentally changes the optical character of the EF 70-200mm f/2.8L IS USM lens. Likewise, even users who are fortunate enough to own one or more EF super-tele lenses may find themselves in situations when it’s imperative to travel light. Yet another reason to consider the 2x Extender with the popular EF 70–200mm f/2.8L IS USM lenses.

With the EF 1.4x Extender, the real asset is that the maximum effective aperture is f/4 — now, fast enough for available-light shooting in many circumstances. Particularly with the outstanding high-ISO image quality now possible on full-frame EOS models, such as the EOS 5D Mark III, EOS 6D and EOS-1D X, f/4 is hardly a limitation in many low-light scenes. So the ability to quickly and easily transform the EF 70–200mm f/2.8L USM lens into an excellent quality 98–280mm f/4 equivalent can make a huge difference when that 200mm just isn’t enough. And once again, on smaller-sensor cameras like the EOS 7D, there’s an additional effective increase in telephoto field of view: that EF 70–200mm f/2.8L USM lens with a 1.4x Extender now “acts” like a 157–448mm f/4 lens. You’re solidly within super-telephoto lens coverage and still preserving a very usable f/4 maximum aperture. The tele converter transforms the optical character of what’s already a very versatile and powerful lens.


Tele extenders aren’t simply for shooters fortunate enough to be working with an EF 400mm f/2.8L IS II USM or EF 600mm f/4L IS II USM lens. Some of their real appeal is how useful and practical they can be with more affordable and popular Canon EF lenses, which are officially compatible with Canon’s EF Extenders. And it’s not a matter of simply increasing the lens’ maximum focal length when you’re shooting in bright outdoor conditions. Lenses like the EF 135mm f/2.0L USM or EF 200mm f/2.8L II USM suddenly become attractive ways to enter the telephoto market when combined with either the EF 1.4x or 2x Extenders — all the more so if they’re used with small-sensor cameras because of the effective increase in telephoto field of view their “crop factor” provides.

But the key point we want to make is how already great lenses can be truly changed in terms of their usability and the imagery they produce with the addition of a tele extender. Again, especially in the case of the 1.4x Extender’s design (because of its modest 1-stop light loss), some users begin to view a lens and extender combination as their “standard” telephoto package, one that can be converted into an even faster, shorter focal-length lens in very low-light conditions by simply removing the extender.

We can’t suggest it strongly enough: even if you’re not a super-telephoto lens owner, consider either (or both) the EF 1.4x and EF 2x Extenders as part of your optical arsenal if you want to change your imagery, especially if you use one of the lenses mentioned in this article.

The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

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