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Discussion Starter · #1 ·
I need some expert advise,

I have recently upgraded to a Canon 5D camera body.
I have a Canon zoom lens EF 100-400mm 1:4.5-5.6 L IS.
I got a Canon Extender 2x II to effectively go to 200-800mm zoom for Christmas.

However, when I put it all together the autofocus doesn't work.

Does anyone know the reason? I read somewhere that it is related to the focal length, but nobody (even the camera store gurus who tend to be very good) can't tell me why.

I also tried the same assembly on my old Canon 300D body with similar results.

As far as the documentation goes, there is no reason it should work.

Thanks,

Tim
 

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Who told you the 2x extender would work on either of those cameras?

I assume the lens alone works correctly on both bodies...
 

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Discussion Starter · #3 ·
The lens itself (without the extender) works perfectly on both cameras. The lens is listed in the supported lens list that came with the documentation for the extender. The only note on bodies I can see in the documentation reads "If you have an EOS A2/A2E/5 and use the extender with any of the lenses listed above, set -1 stop exposure compensation."

The Canon website says that the lens is compatible with the extender also, but not whether there are AF limitations.
http://www.canon.com.au/products/ca...elephoto_zoom_lenses/ef100_400mmlusmlens.html
 

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In the link you posted it does indicate some limits with the extender...

"Compatible with Extender EF 1.4x and EF 2x. With the EOS 3, autofocusing (at the centre focusing point only) is possible while the EF 1.4x is attached to the lens"

I realize you don't have an EOS 3 but it does show there is atleast some issue...

Have you tried the help line listed on the page you linked to?

You might also ask your question here...

http://forums.dpreview.com/forums/forum.asp?forum=1032
 

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linskyjack said:
Have you tried setting the autofocus to the center focusing point and then shooting? Just a guess.
maybe my post was not clear enough on that... :rolleyes:
 

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Actually your post generated my making the concrete suggestion--I have a funny feeling that the poster needs to read the manual in order to figure out how to switch autofocus settings.
 

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I came across this comment and it very well might apply to your situation.
" I use them on my 20D and as long as you can keep 5.6 or less, they will work on AF, but then again, you can manual focus above 5.6 "
 
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