Autofocus problems with the 17-55mm f2.8 IS lens used with the Rebel XT (EOS 350D)

Discussion in 'Digital Photography' started by King Sardon, Sep 6, 2007.

  1. King Sardon

    King Sardon Guest

    My 17-55mm f2.8 IS lens was not autofocusing well with my Rebel XT
    body. Often the focus would end up being way in front of what I
    thought I was focusing on... I mean WAY in front, by maybe 50 ft...
    although it varied.

    My other lenses autofocus well and dependably with the Rebel, but not
    the 17-55mm f2.8 IS.

    I sent the lens in to Canon for them to fix the autofocus under
    warranty. But they returned the lens saying that it was working fine.

    So I tried the lens out on a friend's 20D, and sure enough, the lens
    works fine with the 20D... but not with my Rebel XT. The lens is still
    in its warranty period, but the Rebel is not. Not sure what to do now.
    Does anyone else have this problem with the 17-55mm f2.8 IS lens on
    the Rebel? I'm wondering if it is a design fault or a sample issue.

    King Sardon, Sep 6, 2007
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  2. King Sardon

    Gino Guest

    In the Canon software that came with the camera, does it show the focus
    point that was used for the focus (obviously this will be a bit irrelevant
    if you focused and then recomposed before taking the shot)?

    What focus point settings are selected in camera? All focus points or just
    Gino, Sep 6, 2007
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  3. King Sardon

    King Sardon Guest

    I usually use just one focus point, and usually it is the central one.
    The EXIF doesn't record this... not even whether AF or manual focus
    was used.

    I've done a bunch of tests using focus targets like road signs. They
    are contrasty and flat and should serve this purpose well.

    Oddly enough, all looks normal in the viewfinder, and I get focus
    confirmation on that central point. But when I examine the results
    later, the focus is off.

    King Sardon, Sep 6, 2007
  4. King Sardon

    Brian Guest

    The ZoomBrowser software will show you which focus point was used.

    Brian, Sep 6, 2007
  5. King Sardon

    King Sardon Guest

    I see you are correct -- thanks.

    King Sardon, Sep 7, 2007
  6. Always send in lens AND body.
    You have now experienced _why_.
    Send in lens and body this time. Add shots where you demonstrate
    the misfocussing.
    Most certainly it is not a design fault, or RichA would have been
    jabbering and drooling on it for years, the net would be full of
    it ...

    My guess is that the offset from true focus in your Rebel for
    this lens is scrambled for some reason. Which is why you send
    in the lens and the body, and images showing the problem.

    Wolfgang Weisselberg, Sep 8, 2007
  7. King Sardon

    King Sardon Guest

    Thanks for your advice, which I followed early this morning. The store
    where I bought the body has a very sagacious owner who somehow noticed
    what was going on while I was discussing the problem (again) with one
    of his sales guys. He came up, declared "this is a back focus
    problem", "it's not the lens, it's not the body, it's the interaction
    between them", "happens all the time, including with $10k cameras",

    So body and lens are off to Canon for repairs under warranty.

    King Sardon, Sep 9, 2007
  8. King Sardon

    Rod Guest

    working fine.
    I sent my lens and camera in and am almost certain
    they never checked the lens and camera together.
    Anyway the same problem existed after I got them back.
    Rod, Sep 9, 2007
  9. King Sardon

    Rich Guest

    The lens is so heavy it is bending the body and contact is being lost
    with the electrical lens contacts. Friend had the same issue with the
    heavy Nikon 70-200mm f2.8 zoom and the Nikon D80. Both cameras have
    plastic bodies.
    No problems at all with the Nikon D200 (metal body).
    Rich, Sep 9, 2007
  10. King Sardon

    King Sardon Guest

    Hmm, I support the lens with my hand... also, as I have since
    discovered, the problem occurs equally with manual focus.

    King Sardon, Sep 9, 2007
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