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Thread: Sigma 135-400mm F/4.5-5.6 and teleconverter.

  1. #1

    Default Sigma 135-400mm F/4.5-5.6 and teleconverter.

    I was told that when I put my Sigma 135-400 and a 2X TC together,
    my 350D won't be able to autofocus, since it can't focus on low light
    conditions (>F/6.3).

    What is this parameter in the camera's specification? Any better Canon
    bodies that can do better?

  2. #2
    Senior Member
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    Default Re: Sigma 135-400mm F/4.5-5.6 and teleconverter.

    Ummm, not really any other bodies can do that. When you slap on a 2x teleconverter on a F5.6 lens, it effectively becomes a 800mm F16 on the wide end, and it's very hard for even the EOS-1 series camera to get ANY focus at all.

    Your camera needs light to work... Give it little of that and it won't work.

  3. #3

    Default Re: Sigma 135-400mm F/4.5-5.6 and teleconverter.

    I see, thank you VulpixOr.

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