Canon EF 100-400 f/4-5.6L with 2x extender

[davikokar]

Do you use the 100-400mm in combination with 2x extender ? What do you think about this combination ?

[Bluemoon622]

I have a Canon 7D MkII that I cannot set up to allow AF with the 100-400 + 2x extender. I have tried all the setings mentioned in several articles. I realize there a very few applications for this , but want to be able to access the AF with the extender. Any better ideas other than what I have tried? (menu 4- select AF area, tried with no luck at all modes)

[TCampbell]

The most you should be able to use with that camera (with ANY camera, actually) is a 1.4x extender.

This has to do with how phase-detect auto-focus systems work.  They need light coming to the focus sensor from different angles (normally not a problem with a wide-open aperture) but as you narrow the aperture, the opening is no longer large enough for the light to arrive from angles far enough apart to work.

Most DSLRs can only have working auto-focus on lenses of f/5.6 or less ... but Canon's newer cameras (such as your 7D Mark II) offer support for f/8.

When you use an extender, you must multiply BOTH the focal LENGTH and the focal RATIO by the extender multiplier (e.g. either 1.4 or 2.0).  

So the 100-400 f/4-5/6L becomes a 200-800 f/8-11 (and it's only f/8 at the 200 end ... the moment you zoom in even a tiny bit the aperture is too narrow.

You can still manually focus ... you just can't use auto-focus.

If you used a 1.4x extender then the 100-400 f/4-5.6 becomes a 140-560mm f/5.6-8 lens and that WILL work becuase the wide-open apertures are f/8 or lower for every focal length available.

The 2x extender must not be used with any with a focal ratio higher than f/4.

Also note that there is a slow-down in the speed of AF (always) whenever you use an extender.  This is intentional (normal).

[JesseDd]

The AF works on my 70D in live mode with the 2Xextender, otherwise its manual focus only, the edges are soft when you have the zoom wide open, bad in low light situations, not a great combination in my view.

[enriqupg]

awesome thank you for reporting back- I am glad its working out for you as well - and more importantly for reporting back

[MickvK]

ParadisePhil, to be honest I got tired of having to cart the 2X converter, tripod etc and I bought a 7D MKII which doesn't have the versitile swivel, touch screen. The 70D has been relagated to my 24-105 USM lens. I'd love to buy the new 100-400 USM II lens, it sounds great. Oh the cost of a hobby!

Happy shooting mate. Michael.

[enriqupg]

I am still new to both the equipment and photography - two points
a. if you are going to take videos then its worth it - because you can freeze an image and potentially blow it up - I am sure it wont be as clear as a using the very expensive lenses.
b. if you are looking for super sharp images then its going to frustrate you a lot - to that end I am renting the 200 - 400mm prime lens to see the major difference to compare it to the 100 - 400mm and teleconverter. I wish I could upload pictures and videos

[JesseDd]

Man I glad I read this, I have a Canon 70D I was using with a new 1 to 400 mm EF lens along with a EF 2X loll extender, the Canon tech told me I would have to manually focus with it, so I have been with some real good results most of the time, I tried your suggestion in live mode & the auto focus worked great! This will be a valuable option when I need it, I bought a new 6 D full frame to use wit the lens, extender combo recently as well, works well but I wish it would auto focus like my 70 D does as I use it all the time for wildlife, the auto focus would come in handy, though I'm getting a lot better manually focusing & you can get good results if  a person gets used to using the setup, Many Thanks for the valuable info. Jesse.

[GeorgeM]

I must be doing something wrong. I have “live view” enabled in my EOS 70D and the switch on the back of the camera is set to live view. I am using a 2x ii extender. Autofocus will not work. When I try to focus on an object, the f stop setting is flashing on the display. Any suggestions?

[Waddizzle · Accepted solution]

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@GeorgeMwrote:

I must be doing something wrong. I have “live view” enabled in my EOS 70D and the switch on the back of the camera is set to live view. I am using a 2x ii extender. Autofocus will not work. When I try to focus on an object, the f stop setting is flashing on the display. Any suggestions?

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What shooting mode are you using.  Try using M mode.  How many focus points are you using?  Use just the center one in the viewfinder, and then try Live View, although I do not think that will really help.

The minimum aperture is probably too high.  With the adapter, you will get a minimum range of f/8-11.  You say the f/stop is flashing.  What value of f/stop is it displaying as it flashes?

The EF 2x models are not recommended for use with lenses with minimum apertures exceeding f/4.  The extender instruction manual can tell you which combinations of lenses it is compatible with.  You camera instruction manual should tell you which focus points would be available, which in this case I would expect none to be available in the viewfinder.

[GeorgeM]

I followed your instructions and finally managed to get it to work. I have to manually tweak the focus on the object. After that the autofocus seems to take over. It works that way in both the M and the Av modes. F-stop has to be set at 6 or above. Focusing is a slow process so it’s probably not good for bird photography.