Focusing speed of EF 300mm f/4 with 1.4 TC vs. 400mm f/5.6

Discussion in 'Digital Photography' started by end user too, Feb 11, 2004.

  1. end user too

    end user too Guest

    Re: Focusing speed of EF 300mm f/4 with 1.4 TC vs. 400mm f/5.6

    I know when I put the 1.4 TC on my 70-2000mm f/4 it slows down the AF a bit.

    Q.Is this because of the TC or is it because it's now at f/5.6, or both?
    Would a 400mm at f/5.6 focus AF quicker?
     
    end user too, Feb 11, 2004
    #1
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  2. end user too

    Bill Hilton Guest

    From: "end user too"
    It's because of the teleconverter ... my wife has the 400 f/5.6 L and I have
    the 300 f/4 L and with a 1.4x t/c on the 300 it's noticeably slower to
    autofocus than the 400 f/5.6 even though the nominal aperture is the same. 2x
    is even worse.

    Bill
     
    Bill Hilton, Feb 11, 2004
    #2
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  3. end user too

    end user too Guest

    Bill, do you regularly use filters to cut the haze on the big glass? Which
    ones?

    Thanks again
     
    end user too, Feb 11, 2004
    #3
  4. end user too

    Bill Hilton Guest

    From: "end user too"
    No, I never use filters with these 35 mm tele lenses ... typically I use the
    longer lenses for wildlife so hopefully I'm fairly close, close enough where
    atmospheric haze isn't a problem.

    Here are some typical shots from a nearby National Wildlife Refuge, all with
    lenses from 70-200 f/2.8 up to a 500 f/4 with 2x t/c, no filters on any of
    them, though one was grey-balanced in Photoshop due to a blue cast from a
    cloudy sky.
    http://members.aol.com/hiltonfotography/bosque/harriers_fighting_goose.htm
    (click on the image to go to the entire gallery)

    For landscape shots I typically use medium format and often take a color
    temperature reading and then add the right warming filter to balance the
    colors, especially at higher altitude and in the shade, so if I were using the
    35 mm tele's for landscape I'd probably do that more, but for wildlife I hardly
    ever use a filter.

    Bill
     
    Bill Hilton, Feb 11, 2004
    #4
  5. end user too

    end user too Guest

    Nice shot!

    Thanks again.
     
    end user too, Feb 12, 2004
    #5
  6. end user too

    JPS Guest

    In message <uOsWb.548$>,
    Either the manual to my 300mm f4L IS or my Canon 1.4x says that the
    camera detects the TC, and drops the attempted autofocus speed. I say
    attempted, because if this didn't happen, autofocus might try to be
    fast, bust be slow or fail miserably. It is only slow compared to not
    having the TC on, not compared to if it didn't try to slow down!
    --
     
    JPS, Feb 13, 2004
    #6
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