Canon EF

Updated December 29, 2015 – After using this Extender for several years I thought there are a few things I should clarify, especially since this review does get it’s fair share of traffic. I have added sample images illustrating some of the challenges you should consider when adding this extender to your kit.

Canon Extender EF 2x III

As with anything I write a review, opinion or recommendation about, I prefer to have at least a year and preferably several years of field experience with it. There is a very clear distinction between opinions/reviews based on spec sheets and real world field experiences. Very rarely are they ever perfectly aligned and the internet has no shortage of the former.

The Canon EF 2x Extender is one of the curious items in my kit. It makes for an easy review on a lazy Sunday afternoon so I thought I would share a photographer’s perspective on this lens after at least two years of active use and give anyone thinking about adding this to their kit some important observations to consider before dropping close to $500 on one.

Pros:

Doubles your maximum focal length. Very handy when you get to location and realize your telephoto lens is not quite long enough.
Performs very well when mated to one of Canon’s wide aperture super telephoto primes such as the EF 300mm f/2.8L IS. However one should note this is due to the fact that this lens is incredibly sharp to begin with. Even after 2x magnification, a lot of detail/sharpness/resolution still remains to keep up with a high density sensor such as the Canon 7D Mark II. On a low density sensor such as the 5D Mark III there is still enough detail left when using the 70-200mm f/2.8L IS II lens.
Convenient, relatively light weight. It adds great utility to my kit without the corresponding weight.
Built like a tank. Everything else could be smashed to pieces and this extender will still be hanging onto your lens and camera mounts.

Cons:

Canon EF 2X ExtenderIII – Ghosting at sunset on EF 70-200mm f/2.8L IS II

It is only optically perfect under ideal lighting conditions (lots of light – broad daylight, well lit scene, etc). Anything else will show noticeable chromatic aberration and terrible ghosting as the light has trouble making it through the added layers and the overall light in the frame falls below that from any point sources. Anti-reflective coatings can only do so much.
The only lens I know that will be worth mounting this to is the Canon EF 70-200mm f/2.8L IS II, the EF 300mm f/2.8L IS II or some other L-series lens with an f/2.8 or wider aperture. The extender not only doubles the focal length, it doubles any flaws that lens may have. It also halves the aperture and at that aperture, only the Pro xD Canon DSLRs will be able to acquire focus. You will also need the amazing 4-stop image stabilization on the 70-200mm f/2.8L IS II to manage shake unless it stays tripod mounted.
Even a Pro body that should acquire AF down to f/8 will often hunt considerably. There’s a big difference between stopping your lens down to f/8, asking your camera to acquire AF and slapping this 2x Extender on an f/2.8 or f/4 lens and asking it to find focus. Even though the specs say it should not be a problem, it will be a serious problem. Lighting and contrast conditions must be ideal.
On an APS-C/crop sensor body like the 7D, the higher pixel densities will show noticeable chromatic aberration, often beyond what you can fix in post processing. Again under anything less than ideal shooting conditions.
Price does not match the added capability. In other words, it’s a bit on the pricey side.

Conclusion:

Put put this review in perspective. The EF 2X Extender III is the best possible extender money can buy. However the fact is there is no cheap way to get a longer focal length. You should not rely on an extender to turn 200mm into 400mm. You should consider getting a 400mm or 600mm lens if that is really what you need.

Overall I cannot recommend this lens. This might be of very little use to you unless all your focal lengths in your kit are covered from ultra-wide (16 or 10mm, Full Frame or APS-C respectively) all the way to 200mm and at f/2.8 apertures. If you need 400mm, I suggest you buy a native 400mm lens. I bought mine used at a bargain but at a price close to $500 new, it is hardly worth it. The good news is you don’t have to worry about it being used as it has no moving parts. You may be better off putting your money towards a telephoto prime lens like the 300mm f/4L or one of the other super telephoto L primes or even consider a cheaper third party alternative from Tamron, Sigma, etc.

You can see my previous post about Point Arena Lighthouse for an idea of what constitutes ideal conditions – bright scene with ample color and contrast.

Point Arena Lighthouse

Here is a panoramic of Reagan National Airport I took around sunset. I had to scrap the whole effort because of terrible ghosting as the point lights exceeded the ambient light levels. The ghosting also severely degrades the sharpness of this otherwise impressive lens. This extender is not ideal for use on the 70-200L lenses in low light situations.

Canon EF 2X ExtenderIII – Ghosting at sunset on EF 70-200mm f/2.8L IS II

For a more detailed and objective assessment I recommend reading Bryan Carnathan‘s review of the Canon EF 2x Extender. Allthough his is a more favorable review of the Extender, I still think he’s one of the most comprehensive references out there worth reading.