Canon EF 1.4x III Extender Review

The Canon EF 1.4x III Extender mounts between your Canon EOS Digital SLR and a compatible lens (primarily Canon L Series lenses), extending the focal length of the lens by a noticeable 1.4x. The 1.4x III is a small and light addition to your kit, an only moderate hit on your wallet and it provides a noticeable increase in your focal length. Sounds like a great deal, but this (and all) extenders are not completely without downsides which I'll discuss throughout the Canon EF 1.4x III Extender review.

The primary reason to use any extender is of course to gain a longer focal length/narrower angle of view from a lens – to frame the subject more tightly. Here is an example of the focal length increase provided by the 1.4x and 2x extenders.

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The above images (of a Christmas Cactus flower) were taken from the same tripod-mounted position (using the tripod ring) with a Canon EF 180mm f/3.5L USM Macro Lens on a Canon EOS 5D Mark II camera body. The difference in framing (angle of view) is quite noticeable between the three examples shown. This is the lone, but significant, advantage provided by extenders.

Use of a 1.4x extender (any brand or model of them) decreases/narrows your lens' max aperture setting by 1 stop – allowing at most 1/2 as much light into the exposure. The lens aperture still opens to the same physical diameter, but the ratio of the aperture opening to the focal length is reduced – by 1 stop. So, pick your lens' maximum aperture opening from the following list and understand that it will shift one value to the right when any 1.4x extender is mounted behind it: f/2.0, f/2.8, f4.0, f/5.6, f/8.0, f/11.

Factor in the focal length multiplier and max aperture reduction to get your resulting lens equivalent. For example, a 1.4x extender (also commonly referred to as a teleconverter) makes a Canon EF 70-200mm f/2.8L IS II USM Lens into a 98-280mm f/4 IS lens (yes, IS still functions normally on all compatible IS lenses). A Canon EF 70-200mm f/4.0L Lens mounted over a 1.4x becomes a 98-280mm f/5.6 lens. A Canon EF 300mm f/2.8L IS Lens becomes a 420mm f/4 IS lens. And, as shown in my Canon EF 1.4x III Extender review examples above, the Canon EF 180mm f/3.5L USM Macro Lens becomes a 252mm f/5.0 USM Macro Lens.

DSLR cameras will continue to calculate auto exposures properly when used with Canon extenders.

Though most extender-compatible lenses have max apertures of f/4 or wider, some of the longer ones have an f/5.6 native maximum aperture (such as the Canon EF 100-400mm f/4.5-5.6L IS USM Lens between 260mm and 400mm). DSLR autofocus support of an f/8 max aperture lens and extender combination varies, ranging from not supported at all to supported, though potentially with reduced AF point capability. The lens and extender combo can always be used in manual focus mode, but remember that a narrow max aperture creates a dark viewfinder that makes manual focusing difficult. Often better (when available) is to use Live View AF, which is generally supported even with f/11 max aperture lens combinations.

Extenders do not affect the MFD (Minimum Focus Distance) of the lens they are mounted behind, so the MM (Maximum Magnification) of the lens is also multiplied by 1.4x. Do you need more macro magnification from your Canon EF 180mm f/3.5L Lens? Add the Canon EF 1.4x III Extender to the setup for a 252mm 1.4:1 (1.4x) Macro lens.

Shooting with the Canon EF 1.4x III Extender mounted results in reduction of autofocus speed. According to Chuck Westfall (Canon USA): "As with previous EF Extenders, usage of Series III EF Extenders lowers AF drive speed to improve AF performance. When Extender EF 1.4X III is used, AF drive speed is reduced by 50%. When Extender EF 2X III is used, AF drive speed is reduced by 75%. This may seem like a drawback, but in reality subject tracking performance remains quite high when Series III Extenders are used with IS II lenses. This is due to improvements in AF precision made possible by the new microcomputer in the extenders."

Canon's Rudy Winston completes this story:

"Because AF systems are essentially computer-controlled to read and react to focus distance changes, the information must be modified so that the focusing movement (or sensitivity) compensates for the added presence of the extender. In the Canon EOS system, this is done by deliberately reducing drive speed when an extender is detected.

Before you immediately conclude that this is a problem, understand that this reduction in drive speed now corresponds to the effective speed you would achieve with the same EF lens alone. It compensates, automatically, for the reduced distance lens elements in the lens’s focusing group(s) need to move to refocus on a subject, with either EF Extender in place. Accordingly, overall AF performance remains essentially unchanged with an EF Extender attached, versus the lens’s AF speed without an extender."

With good lenses mounted, I'm not having any trouble with 1.4x III AF speed. AF is always going to be more challenged if you are shooting in very low light, shooting fast-approaching close subjects and/or using a slow-focusing lens.

The biggest downside to using an extender, in my opinion, is the image quality reduction it causes. Because the Canon EF 1.4x III Extender is magnifying the aberrations/flaws of the lens it is mounted behind by 1.4x and because there are now 7 additional lens elements for light to pass through, some reduced image quality should be expected. Perhaps the biggest surprise is how little the degradation is.

The image quality of lenses varies from model to model; and therefore, the optical results of the various with-extender combinations also vary. A great lens will typically produce the best image quality when used with the 1.4x and the best way to see how specific extender+lens combinations perform is by using the ISO 12233 Resolution Chart Tool. All current extender-compatible lenses have ISO 12233 chart results from the with-extender combinations available (select the with-extender focal length value). Compare the native maximum focal length to the extended focal length to see the optical change from the combination.

The Canon EF 1.4x III Extender reduces contrast and sharpness somewhat. Stopping the lens down one to two stops usually improves the image quality of both the bare lens and the extended lens combination.

The 1.4x III adds some barrel distortion to the lens it is being used with. Since many telephoto zoom lenses have pincushion distortion at their longest focal lengths, the added barrel distortion can counter the pincushion distortion to some extent. Note that barrel distortion causes the center portion of the image (top image in the ISO 12233 tool) to be slightly enlarged, which can make it appear to resolve more detail.

I am seeing a little more CA (Chromatic Aberration) in the corners of some extender and lens combinations. Using the center of the image circle allows vignetting to be somewhat reduced.

The Canon 180 L Macro is a lens that performs very well with extenders. Shown below are 100% resolution crops taken from the example shown earlier in the Canon EF 1.4x III Extender review that show the results of what this very sharp lens, stopped down to f/11 and used with studio lighting can produce with extenders.

Each row below the image represents either the bare lens or the lens with the specified extender mounted behind it. In each row, the left-most mouseover label is the native resolution of the combination and the values to the right show Photoshop CS5 up-rezzed (resized larger) images created from the native image.

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It is obvious that extenders produce better results than simply increasing the size of an image in Photoshop (and this is of course only true when you do not want the entire native lens' Field of View). Also impressive is the resulting image quality in these extender examples. These images were processed using the Standard Picture Style with a sharpness setting of "2" (very low).

As a rule, but subject to change, the Canon lenses compatible with the Canon EF 1.4x III Extender include fixed focal length L lenses with focal lengths of 135mm and longer, zoom L lenses with at least 70mm of focal length on their wide end (the Canon EF 70-300mm f/4-5.6L IS USM Lens excluded). Canon TS-E Tilt-Shift lenses are not included on Canon's official compatibility chart and do not have the 3 additional gold lens contacts for communicating extender information to the camera, but as their image quality results shown on their reviews show, they can function with extenders. The following list of discontinued lenses fitting these parameters are compatible, but may require camera microfocus calibration for accurate focusing (note that not all DSLR cameras support microfocus calibration):

Canon EF 200mm f/1.8 L USM Lens
Canon EF 300mm f/2.8L USM Lens (non-IS)
Canon EF 400mm f/2.8L USM Lens (non-IS)
Canon EF 400mm f/2.8L II USM Lens (non-IS)
Canon EF 500mm f/4.5 L USM Lens
Canon EF 1200mm f/5.6L USM Lens

Due to having incompatible signal relay systems, film SLRs are not compatible with the Series III Extenders (with the EOS-1V being the only exception).

While some third party extenders *may* work properly with Canon's non-extender-compatible lenses, they probably will not report the reduction in aperture. Attempting to mount a Canon extender on these same non-compatible lenses can damage the lens due to contact being made with the rear lens element. Canon extenders simply do not fit behind the rear lens element on Canon's non-extender-compatible lenses.

The Canon extenders have a protective rubber ring around the front element to protect both the extender itself and the lens it is being inserted into if your alignment is off when mounting the extender to a compatible lens.

As I said earlier in the Canon EF 1.4x III Extender review, the III replaces the II. My first order of business upon purchasing (retail) my 1.4x III was to add the with-extender-III ISO 12233 resolution chart results to all of the current extender-compatible lenses. The same lenses have results from the version II extenders and provide a lens-by-lens basis for comparisons between the two extender versions. The series III extender results are the last set of focal lengths available for each lens. Here is the list of these lens reviews – which is also the comprehensive-at-review-time list of currently available extender compatible Canon lenses. Always check the Lens Specifications and Measurements Tool for the most update-to-date compatibility specs.

Canon EF 70-200mm f/4.0L USM Lens
Canon EF 70-200mm f/4.0L IS USM Lens
Canon EF 70-200mm f/2.8L USM Lens
Canon EF 70-200mm f/2.8L IS II USM Lens
Canon EF 100-400mm f/4.5-5.6L IS USM Lens
Canon EF 135mm f/2.0L USM Lens
Canon EF 180mm f/3.5L USM Macro Lens
Canon EF 200mm f/2.8L II USM Lens
Canon EF 200mm f/2.0L IS USM Lens
Canon EF 300mm f/4.0L IS USM Lens
Canon EF 300mm f/2.8L IS USM Lens
Canon EF 400mm f/5.6L USM Lens
Canon EF 400mm f/4.0 DO IS USM Lens
Canon EF 400mm f/2.8L IS USM Lens
Canon EF 500mm f/4.0L IS USM Lens
Canon EF 600mm f/4.0L IS USM Lens
Canon EF 800mm f/5.6L IS USM Lens
Canon TS-E 17mm f/4L Tilt-Shift Lens
Canon TS-E 24mm f/3.5L II Tilt-Shift Lens
Canon TS-E 45mm f/2.8 Tilt-Shift Lens
Canon TS-E 90mm f/2.8 Tilt-Shift Lens

The image quality differences most easily noticed between the 1.4x II and the 1.4x III are:

The 1.4x III has less barrel distortion than the 1.4x II. This makes the center-of-the-frame details slightly smaller in a comparison. This difference will be most noticeable in the top crop shown in the ISO 12233 chart tool.

Anomalous dispersion glass elements are used in the Series III extenders to reduce chromatic aberration and increase resolution and contrast. The CA difference between the II and III is quite noticeable – pay close attention to this difference in the bottom ISO 12233 crops.

Less noticeable are the resolution and contrast differences, but some comparison examples do show improvements.

Contributing to the improved image quality is Canon’s Super Spectra coating which reduces ghosting and flare. Front and rear elements have Canon's fluorine anti-smear coating – making them very easy to clean.

Not available as I create the Canon EF 1.4x III Extender review are the announced:

Canon EF 300mm f/2.8L IS II USM Lens,
Canon EF 400mm f/2.8L IS II USM Lens,
Canon EF 500mm f/4L IS II USM Lens and
Canon EF 600mm f/4L IS II USM Lens.

Improvements in the Series III extenders promise to perform especially well on these specific lenses.

A microcomputer integrated into the Series III Extenders promises faster autofocusing and increased AF precision when used with the Canon IS Supertelephoto Series II lenses mentioned above and (I expect) all future compatible lenses. Better optical quality is also expected.

Note that "AF precision remains the same as the Series II Extenders when the Series III Extenders are used with earlier extender-compatible EF lenses." [Canon]

Note that Canon does not recommend stacking extenders. While they do not fit together due to the lack of space at the rear elements, an extension tube installed between them can be used to make the fit possible. But, Canon does not recommend using ETs at all due to reduced autofocus accuracy. Image quality from stacked extenders will not be great.

Let's take a look at the Canon EF 1.4x III Extender mounted on a camera body.

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The Canon EF 1.4x III Extender increases the physical length of any combination it is used with by 1.07" (27.1mm) and increases the weight by 8 oz (225g). The 1.4x III grew .4 oz (12g) heavier than, and remains essentially the same length, as the Canon EF 1.4x Extender II it replaces.

Two additional lenses in 1 less group (7/3 vs. 5/4) are found in the III (and likely contribute to the slightly increased weight). The mounted extender also shifts the lens weight forward slightly for a potentially small change of balance. The zoom and focus rings are of course shifted away from the camera body the same amount as the lens. Overall, the handling change caused by the 1.4x extender is minor and the additional magnification is nice.

Below are the Series II and III Extenders shown for comparison.

Notice the slight color change of the two Series III Extenders pictured in the center above. The new color matches Canon's latest white L lenses.

Model	Weight		Dimensions w/o Hood		Year
Canon EF 1.4x III Extender	7.9 oz	(225g)	2.8 x 1.1"	(72 x 27.2mm)	2010
Canon EF 1.4x II Extender	7.8 oz	(220g)	2.9 x 1.1"	(72.8 x 27.2mm)
Canon EF 2x III Extender	11.5 oz	(325g)	2.8 x 2.1"	(72 x 52.7mm)	2010
Canon EF 2x II Extender	9.4 oz	(265g)	2.8 x 2.3"	(72 x 58mm)

Like the 1.4x II, the Canon EF 1.4x III Extender is weather-sealed and very-solidly-built - similar to Canon L Lenses in construction quality. The Series III extenders include some durability improvements.

The lens mount pin and lens mount stopper pin are improved for higher endurance and, as you can see below, there are now 7 (instead of 4) screws holding the rear lens mount to the body.

Considering that an extender can have nearly $20,000 worth of camera and lens attached to it, the extra strength insurance can be appreciated. The lens mount release switch received a cosmetic upgrade, but functions the same.

At review time, the price differential between the still-available version II extenders and the version IIIs is rather high. If the prices were equal, there would be no question that the III is the extender version to get. But, saving money is one of the reasons to buy an extender instead of a lens with a longer native focal length. And I'm sure that not everyone can justify the cost difference to go with the 1.4x III over the 1.4x II.

Of course, to get an extender at all is the first decision to make. The image quality penalty of the 1.4x is not bad – it can be a good option for many.

My advice is to use the Canon EF 1.4x III Extender to extend the usefulness of a sharp lens that has another more primary purpose. Buy a lens with the native focal length you need for best results. Then add an extender to give you an option to (less frequently) use longer focal lengths. Said another way, you generally will get better results from a 300mm lens than with a 200mm lens plus the Canon EF 1.4x III Extender, but being able to shoot at 280mm or 420mm is a nice option.

Another good reason to use an extender is to create a longer focal length lens than is available natively. For example, a Canon EF 800mm f/5.6L IS USM Lens plus a 1.4x results in a not-natively-available 1120mm f/8 IS USM Lens.

Buying an extender over a longer lens for financial reasons can also make sense. The very long focal length lenses are considerably more expensive than extenders.

Using extenders to save space when traveling or hiking can be a good decision.

What types of photography are extenders used for? Sports and wildlife are two of the most common photography pursuits utilizing extenders. Photojournalism, law enforcement and many other types of photography can also make good use of them.

While I don't use extenders a big percentage of the time, I often have the Canon EF 1.4x III Extender along with me. The Canon EF 1.4x III Extender extends the reach of your sharp and compatible Canon lenses for a small image quality penalty and a relatively low size, weight, and financial cost.