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Old 27th of June 2011 (Mon)   #1
jiimybelll
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Default 7D+100-400+2xlll Extender

Trouble with AF, 100-400 lens listed to work with the 2x,
any help would be greatly appreciated,
Jim
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Old 27th of June 2011 (Mon)   #2
1Tanker
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Default Re: 7D+100-400+2xlll Extender

What's your trouble.. won't auto-focus? The 100-400 won't AF on any camera with a 2x extender, and only on 1-series bodies with a 1.4x(unless you tape the contacts).
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Old 27th of June 2011 (Mon)   #3
phreeky
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Default Re: 7D+100-400+2xlll Extender

What he said ^^^

Except it should AF in liveview, if you really need it. But in my experience the results in liveview aren't consistent if you can't stop the wobble (i.e. on very steady support).
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Old 27th of June 2011 (Mon)   #4
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Default Re: 7D+100-400+2xlll Extender

AF definitely wont work but MF will with & without support as depicted below.

5D MKII + 400L prime + Kenko 2x MC4 DGX at 800mm/f11.0 + monopod :

http://photography-on-the.net/forum/...postcount=1850

7D + 100-400L + Kenko 2x MC4 DGX at 800mm/f11.0 + handheld :

http://photography-on-the.net/forum/...d.php?t=983021

I primarily limit my personal use to the 1.4 TC and tape the pins on any fixed f5.6 lens but it can be fun to play around with the 2X extenders when ambient lighting conditions are favorable to achieve some success using MF.

Regards,
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Old 27th of June 2011 (Mon)   #5
bpark42
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Default Re: 7D+100-400+2xlll Extender

Quote:
Originally Posted by jiimybelll View Post
Trouble with AF, 100-400 lens listed to work with the 2x,
any help would be greatly appreciated,
Jim
First, I would stay away from using a 2x converter on the 100-400. The image quality will suffer significantly, especially on the 7D.

Anyhow, the 7D will not autofocus if the max f-stop of the attached lens is higher (smaller aperture) than f5.6. With a 2x TC on the 100-400 your f-stop is effectively f11 so you are out of luck. Even with a 1.4x you would be at f8 and still out of luck.

Your only option is to tape the pins to prevent the converter from reporting itself to the camera. If you do this the camera will attempt AF but it may not work very well since not enough light is getting to AF sensors.

Oh, and the fact that the converter is listed as "compatible" with the 100-400 simply means that it fits and can be used. It does not mean AF will work.
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Old 27th of June 2011 (Mon)   #6
Jim K
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Default Re: 7D+100-400+2xlll Extender

I don't think that was Canon that said the 2x converter would work on the 100-400, at least without saying it won't autofocus.
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Old 27th of June 2011 (Mon)   #7
phreeky
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Default Re: 7D+100-400+2xlll Extender

Quote:
Originally Posted by bpark42 View Post
If you do this the camera will attempt AF but it may not work very well since not enough light is getting to AF sensors.
It's rarely the amount of light that is the problem, it's the aperture being too small and the way phase detection works that is the real problem.
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Old 28th of June 2011 (Tue)   #8
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Default Re: 7D+100-400+2xlll Extender

I love my 100-400, but I do not use telextenders with it. Too much hassle for poor performance. I just crop the native lens and feel it works as good as or better than the poor performance with a converter, especially the 2x. Now the 400 f2.8L may take a 2x ok, but then one needs a tripod and a large first cost,, so I just get what I can without converters and realize it is still the best performing lens in its class.
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