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Topic: CANON 1.4X EXTENDER ? (Read 7574 times)
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dem74
Newbie
Posts: 10
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Will I lose AF on the Canon EF 70-200mm f/4.0 L USM Lens & the EF 400mm f/5.6L USM? I have the 50D...
Thanks
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Bob Atkins
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The Canon EF 1.4x will be fine on the EF 70-200/4L. You will have AF at all focal length settings. The lens will become a 98-280/5.6 zoom On the EF 400/5.6L you will lose AF with the 1.4xTC. While there are some tricks you can try (involving covering up some of the pins on the TC), they usually result in unreliable AF and/or lots of hunting for focus. |
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« Last Edit: September 30, 2009, 02:06:49 PM by Bob Atkins »
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dem74
Newbie
Posts: 10
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How about the 2x on the 70-200mm bob? i 4got to ask...
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Bob Atkins
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Nope, no AF with a 2x
Basically you need f5.6 to AF on the 50D. A 1.4x adds 1 stop so f4 becomes f5.6 which is fine. A 2x adds two stops so f4 becomes f8, which means no AF.
It's the same for all Canon bodies except the EOS 1 and 1D series and the EOS 3 film body. Those bodies will AF at f8. In the digital line the Rebels, the 10/20/30/40/50D, the EOS 7D and the EOS 5D (MkI and MkII) all cut off at f5.6.
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