Canon 70-200mm F2.8 With 1.4 Extender

Discussion in 'Digital Photography' started by Russell, May 8, 2005.

  1. Russell

    Russell Guest

    According to Canon's instructions:

    "If an extender (optional) is attached and the maximum aperture of the lens
    is f/5.6 or smaller, AF will not be possible. For details, see the
    Extender's instructions."

    Does that mean you loose Auto Focus when using a Canon 70-200mm F2.8 with
    1.4 Extender? Or does AF work, but only from F8 and smaller (F5.6, plus the
    1 stop loss from the converter).

    Anyone know why this is?
    Russell, May 8, 2005
    #1
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  2. Russell

    C Wright Guest

    On 5/8/05 8:49 AM, in article , "Russell"
    <> wrote:

    > According to Canon's instructions:
    >
    > "If an extender (optional) is attached and the maximum aperture of the lens
    > is f/5.6 or smaller, AF will not be possible. For details, see the
    > Extender's instructions."
    >
    > Does that mean you loose Auto Focus when using a Canon 70-200mm F2.8 with
    > 1.4 Extender? Or does AF work, but only from F8 and smaller (F5.6, plus the
    > 1 stop loss from the converter).
    >
    > Anyone know why this is?
    >
    >

    You are trying to make it too complicated! The lens always focuses at
    maximum aperture, then stops down when the shutter button is pressed. So
    the only thing that you need to be concerned about is the maximum aperture
    available. The 1.4 extender will cost you one stop so your f2.8 lens will,
    in effect, become an f4 lens. That is enough aperture for auto focus to
    always work.
    Chuck
    C Wright, May 8, 2005
    #2
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  3. Russell

    [BnH] Guest

    What Teleconverter are you buying ? Is it this one ?
    http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=220456&is=USA

    There is a few limitation . .but the AF still works.

    =bob=


    "Russell" <> wrote in message
    news:...
    > According to Canon's instructions:
    >
    > "If an extender (optional) is attached and the maximum aperture of the
    > lens
    > is f/5.6 or smaller, AF will not be possible. For details, see the
    > Extender's instructions."
    >
    > Does that mean you loose Auto Focus when using a Canon 70-200mm F2.8 with
    > 1.4 Extender? Or does AF work, but only from F8 and smaller (F5.6, plus
    > the
    > 1 stop loss from the converter).
    >
    > Anyone know why this is?
    >
    >
    [BnH], May 8, 2005
    #3
  4. Russell

    Bill Hilton Guest

    >"If an extender (optional) is attached and the maximum aperture of the

    >lens is f/5.6 or smaller, AF will not be possible.


    This is true for the consumer cameras, but with the Pro models like the
    1Ds and 1D series it's f/8.

    >Does that mean you loose Auto Focus when using a Canon 70-200mm
    >F2.8 with 1.4 Extender?


    No, because the "max aperture" is f/4 with this combo. You can also
    use the 2x and the max aperture is f/5.6. It means you can't put the
    1.4x on an f/5.6 lens and AF or the 2x on an f/4 lens and AF, that's
    all.

    >Or does AF work, but only from F8 and smaller ...


    It will AF with the lens wide open and then stop down to the desired
    aperture when you actually take the shot. So you can set it for f/32
    but with the 1.4x or 2x t/c on the f/2.8 lens it will still AF, because
    focussing takes place while the lens is wide open.

    >Anyone know why this is?


    Because the body needs a certain amount of light and contrast to
    autofocus reliably.

    Bill
    Bill Hilton, May 8, 2005
    #4
  5. Russell

    Marius Guest

    Marius, May 8, 2005
    #5
  6. Russell

    Russell Guest

    Cheers all.


    "Russell" <> wrote in message
    news:...
    > According to Canon's instructions:
    >
    > "If an extender (optional) is attached and the maximum aperture of the

    lens
    > is f/5.6 or smaller, AF will not be possible. For details, see the
    > Extender's instructions."
    >
    > Does that mean you loose Auto Focus when using a Canon 70-200mm F2.8 with
    > 1.4 Extender? Or does AF work, but only from F8 and smaller (F5.6, plus

    the
    > 1 stop loss from the converter).
    >
    > Anyone know why this is?
    >
    >
    Russell, May 8, 2005
    #6
  7. "Bill Hilton" <> wrote in message
    news:...
    > >"If an extender (optional) is attached and the maximum aperture of the

    >
    >>lens is f/5.6 or smaller, AF will not be possible.

    >
    > This is true for the consumer cameras, but with the Pro models like the
    > 1Ds and 1D series it's f/8.



    Ding, ding , ding! Finally the correct answer.
    Dave R knows who, May 9, 2005
    #7
  8. Russell

    Guest

    In message <427e611f$0$803$>,
    "Marius" <nieuws*takeaway*@hrl.dosgg.nl> wrote:

    >Fred Miranda gives a solution for the autofocus limitations of
    >teleconverters:
    >
    >http://www.fredmiranda.com/TipsPage/


    Of course, AF can become very slow and very inaccurate when forced to
    work with a TC.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
    , May 13, 2005
    #8
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