Canon Extender EF 1.4x III & Extender EF 2x III


Tele-extenders are terrific tools for increasing the focal length of your current lenses without taking up valuable space or adding additional weight to your camera bag, and if you're a Canon shooter, you might be interested to know about the new Extender EF 1.4x III and Extender EF 2x III tele-converters.

Canon's Extender EF 1.4x III and Extender EF 2x III multiply the focal lengths of most Canon normal, macro and telephoto lenses by a factor of 1.4x and 2x respectively. Both extenders contain built-in microcomputers that provide seamless functionality between Canon (D)SLRs and lenses. Other features found on and within each of these new  tele-extenders are Fluorine lens coatings and weather and dust-proof construction. The Canon Extender EF 1.4x III and Canon Extender EF 2x III are expected to be available in December, 2010, for an approximate retail price of $500.

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Can the Canon Extender EF 1.4X or EF 2x Extender be used with a Canon Eos 24-105L lense?

Unfortunately, none of the Canon teleconverters are compatible with the EF 24-105mm f/4.  You would not be able to use a teleconverter with that lens.

I have actually used the 2x III extender with the 28-300. You have to manual focus and you MUST be dilegent to keep the lens longer than 50mm or you will impact the rear element into the extender. I help protect against this by using the tripod mount ring and clamp it on at the 70mm line.

For me the purpose of the extender is to get me out in the 400-600 range so I'm never less than the 200 anyway or I'd just leave the lens stock. I found the 70 line to be a good balance point for me. I just slip a business card in the ring to help it 

I found this out as I had the extender for another lens and figured I'd fiddle with it, not wanting to buy another. Because I actually liked the 28-300 so much I got ride of the other lens and kept these two since I found a work around for the incompatibility. I just can't afford another L series lens, and the flexibility of this one is just to great to part with. 

I am certain this should not be a practice for many or even most, however I did find I could get it to work and got the extra range out of the lens. Anyhow, just thought I'd mention that. 

Perhaps it might help someone. Do be clear though, you will have to manual focus. 

I currently have a Canon 1.4x first generation, and also a Kenko 1.4x 300 DG. I've found that the Kenko is slightly better than the Canon 1st generation.

I use extenders mostly with the Canon 70-200 f4 IS L lens, and have been using the Kenko mostly.

I know that the electronics of the new Canon 1.4x will not give any benefit over my current extenders, but will the optical quality be better?

I have been able to use liveview autofocus with a 300 f/4 with a 1.4 & a 2 stacked on my 5Dm2.  It isn't very fast, but once you pre-focus, you can take pictures like normal.  You can also zoom in with the liveview LCD on the back to see if things are in focus, but I think Canon needs to have a 25x and a 100x mode to make sure things are in perfect focus.  You just need a really stable tripod and not touch the camera (or it is too blurry from camera shake), which is a problem when it comes to changing the focus.

i'm just wondering if there will be any image quality improvments over the second generation using a 300mm prime?  Or I'm also starting to get into telescope and astrophotography, and I'm wondering if using these with a telescope will help zoom in optically.

 I just got an e-mail from the manufacturer's customer service site which stated that the 2X III extenders will be shipped to the main retailers by December 13.


lynn Amaral wrote:

But do we know which camera bodies the autofocus will work with??

Is there a similar list for which bodies they work with? i.e. 1DMii or 70d?


It's all pretty simple. The reason the AF ceases to work with an extender attached is not that the extender isn't capable of AF function or that it disrupts any AF signal or something like that. The reason is that the camera's AF sensors need a maximum f-stop number to function. This is f/5.6 for all EOS except the 1D series, and f/8 for all 1D cameras (but only the center AF point will work as a line sensor in that case).

So what you have to do to figure out if the AF will work with an extender is simple: You take the lens's f-number at the maximum focal length and multiply it with the extender factor (1.4x or 2x). If the resulting number is <= 5.6, then AF will work, if it's larger, it won't (except on 1 series, see above).

Matt wrote:

how many stops of light will you lose by having one of these attached - I shoot primarily with 1.2's and 1.4's so am concerned about losing too much by attaching this, but would love the extra reach on an 85 1.2 per say.  Any idea what the difference would be in terms of loss?

The extenders won't work on fast primes like the 85/1.2. It can't be connected physically. The shortest prime it can be used with is the 135/2L.

Besides that, using an extender on a short prime or even zoom lens (which is possible using 3rd party extenders) normally doesn't yield good image quality. In most cases even just cropping your image gives you better results.

I was real interested in the 2X extender III , as I just purchased a Canon 7D with the 100-400mm lens. Unfortunately, I just received an email back from Canon stating that unless you have an EOS 1 series camera, this extender will not do autofocus. If you have a 1 series camera it works only on the center AF point. As a previous poster stated, the lenses that it works with are listed at the Canon website. Canon will begin shipping these in late December and probably will be available in January. 

how many stops of light will you lose by having one of these attached - I shoot primarily with 1.2's and 1.4's so am concerned about losing too much by attaching this, but would love the extra reach on an 85 1.2 per say.  Any idea what the difference would be in terms of loss?

As someone else posted above, here is the compatibility list:

It's a shame the new EF 70-300 f/4-5.6L IS isn't compatible.

Anonymous wrote:

As someone else posted above, here is the compatibility list:

It's a shame the new EF 70-300 f/4-5.6L IS isn't compatible.

But do we know which camera bodies the autofocus will work with??

Is there a similar list for which bodies they work with? i.e. 1DMii or 70d?


 Does anyone know where you can buy one of these?  All I can find online is the version II, not the version III extender.

Any official words yet on camera compatibility? 

I have a Canon 50D with a 70-200mm f/4 L IS.  Will I lose functionality with one of these new extenders?  Is it worth it?


Who goes wide with an extender on? Please note: Just a bunch of speculation based on no personal experience follows! I wouldn't buy the combination until we've at least seen the mechanics (not to mention the results) of it, but I'm guessing you might be able to take off the extender when you need the wide end again (or, ideally, you only put on the extender when you anticipate you'll need to go beyond 300mm; sacrificing aperture all the time seems distasteful). It's not as seamless a solution as the 28-300mm itself, but you still are keeping it down to essentially one lens in your kit.

That all depends if I'm working on the right assumptions. The big question for me, which I hope somebody can fill me in on, is how the lens operates. My experience is mainly with primes where the focusing is internal near the back of the lens - getting closer as you focus to infinity, farther when you focus closely. The 28-300mm is a push-pull design so I would assume that changing the focal length from tele to wide may not move the groups near the back of the lens much closer to the film plane. Is this on the mark or off? Only zooms I've got sitting around are some super cheap ones with rotating front elements - and the front element goes farther out at wide AND tele, coming in a bit for the middle of the range. (Examples are the Nikon D3000 kit lens and the EF 28-90mm III for the Rebel 2000 film SLR).

For the speed - I think this combination would make an excellent "travel lens" for landscapes and architecture. Even without an extender, the f/5.6 aperture doesn't seem fast enough for action, though I would be tempted to try it for bird photos.

I certainly hope that these extenders will be compatible with the 70-200 f/4 IS and the 100-400 IS.  Does anybody know for sure whether autofocus will work with these lenses.  Obviously, they don't work with the II series, but is the III series able to do this?   Definite word would be welcome here, rather than best guesses. 

These extenders have all of the penalties and restrictions of previous extenders. They will not fit most lenses as the protruding front element prevents mounting many EF lenses. Here is a link to Canon's list of compatable lenses:

The article also explains that these extenders are optimized for the newest generation of super-tele lenses. Even if your lens fits, it will not be optimized for these extenders.

It is important to understand that an "F stop" is ascertained by calculating the ratio between the diameter of the aperture at the back of the lens, to the length of the tube to the front element. By adding an extender ( 1.4x or 2.0x ) you lengthen the tube and the ratio changes to a greater number.

The 1.4x will increase that radio  by one unit F stop. The 2.0x will increase it by two F stops.

Any lens which goes beyond f5.6 will function, but lose the auto focus functionality. You will also start to lose image quality with a 2.0x extender....and yet the 1.4x maintains image quality....This is a huge subject and impossible to cram into a few short paragraphs......Read up about it all over the Internet. Very interesting and it will improve your results...

Generally a rule-of-thumb is NOT to use extenders on zoom lenses, and just stick to using them on prime lenses.

Hope this helps

I have the type II versions of these extenders and would like to know, exactly, what is the "seemless functionality" these new models offer?

I would assume, "microcomputer controlled" can not change the basic optical limitations of any extender (reduction of maximum aperture and magnification of any optical errors in the lens it is used with).

The camera body "knows" which extender is being used when  type II extenders are attached to it and reflects their presence in the maximum aperture that may be used. The loss of light is dealt with by the camera's metering system as it would be with any light-reducing situation. If the extender's use results in a maximum aperture beyond f/5.6 then manual focusing must be used (with the 5D and 10D, anyway).

Are any of these things different now with the type III extenders? 

 I really hope they are compatible with the EF 28-300mm.  fingers crossed :)

the lens group and elements count have increased in both teleconverters

each will be heavier than the series 2

i asked canon this morning and they say available December 1, 2010

i ordered the 2x just yesterday to use with my 70-200 2.8 IS Series 2 for next week's US Open Tennis Championships

The extenders are probably the only items I may be able to afford buying in this round of product updates.

What lenses are they compatible with?  I really need this for the Canon 24-105 L IS USM lens, and can't find one anywhere.

Are They Compatible with the Canon Ef 70/200 L USM Lens

 Are these new extenders compatible with the 

Canon EF 28-300mm f/3.5-5.6 L IS USM