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Thread: Auto focus function with Canon 1.4X III extender

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    Default Auto focus function with Canon 1.4X III extender

    Hi. If I use a 1.4X (mark 3 latest) extender with an L series 100-400 4.5-5.6 EF lens of canon, will I lose the auto focus function? Thanks for any input.

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    When you use the 100-400 lens with a 1.4x TC, the aperture becomes f8. So you will lose auto focus function with all cameras except the 1 series cameras. In the 1 series cameras (except the yet to be launched Canon EOS 1DX), you can use the centre AF point to auto focus. If I remember right you were using a 7D. In the EOS 7D camera, you will lose auto focus and have to manually focus if you use the 1.4x (I, II, III versions).

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    Default Thanks

    Thanks a lot. I am told that we have to mask 3 pins using a tape so that auto focus will work on 7D..


    Quote Originally Posted by Sabyasachi Patra View Post
    When you use the 100-400 lens with a 1.4x TC, the aperture becomes f8. So you will lose auto focus function with all cameras except the 1 series cameras. In the 1 series cameras (except the yet to be launched Canon EOS 1DX), you can use the centre AF point to auto focus. If I remember right you were using a 7D. In the EOS 7D camera, you will lose auto focus and have to manually focus if you use the 1.4x (I, II, III versions).

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    Quote Originally Posted by Sabyasachi Patra View Post
    When you use the 100-400 lens with a 1.4x TC, the aperture becomes f8. So you will lose auto focus function with all cameras except the 1 series cameras. In the 1 series cameras (except the yet to be launched Canon EOS 1DX), you can use the centre AF point to auto focus. If I remember right you were using a 7D. In the EOS 7D camera, you will lose auto focus and have to manually focus if you use the 1.4x (I, II, III versions).
    It works as follows:

    http://www.michaelfurtman.com/taping_the_pins.htm

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    The pin taping is a popular trick which works well for some and not so well for others. If you are in a safari, then better to rest the lens on the vehicle and use the manual focus ring to fine tune the focus.

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    Thanks Sabs. I learnt another thing. I am using a 1.4X mark III extender of canon. When i mask the three pins, auto focus slows down but aperture does not drop !!! Picture quality is excellent.

    If i don't mask then auto focus goes away and aperture drops by 1 stop.

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