Focus out of whack on Canon 135mm f/2.0 L?

Manfr3dManfr3d Registered Users Posts: 2,008 Major grins
edited May 21, 2011 in Cameras
Hi,

When I prefocus my lens to close focus and then press the AF button the
focus is dead on. But when I put the lens to infinity focus and then let the
AF do it's work the lens visibly misfocusses.

I did some tests + tripod that show the problem. Focus was on the "e".

1. Starting from infinity
_MG_3696.jpg

2. Starting from near focus
_MG_3697.jpg

This can't be normal, can it?
“To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
― Edward Weston

Comments

  • ziggy53ziggy53 Super Moderators Posts: 24,129 moderator
    edited May 11, 2011
    Without seeing the full EXIF it's hard to know what's happening with this set of images. Please repost the images with full EXIF so that I can review the camera settings. The settings might indicate something or help understand what's going on here.

    My own copy of the EF 135mm, f2L USM is not terribly accurate to AF at close focus distances. I use Live View mode and magnification for best results at close distances. I consider this normal behavior.
    ziggy53
    Moderator of the Cameras and Accessories forums
  • Manfr3dManfr3d Registered Users Posts: 2,008 Major grins
    edited May 11, 2011
    Settings are for both images the same.

    5D II on heavy duty tripod with MLU and 2sec timer.
    Center af point only, one shot mode
    Manual mode, f/2.0, 1/30s, ISO 100.
    No in camera focus adjustment
    Same lighting in both frames.

    The results are reproducable meaning that the
    differenc between first and 2nd focus attempt
    are always the same.

    I did this the test because many images shot handheld
    in other modes also had a slight backfocus where others didn't.

    I have played with in camera focus adjustment which allowed me to
    get rid of the backfocus at the cost of introducing a front focus
    for the other shots.
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
  • ziggy53ziggy53 Super Moderators Posts: 24,129 moderator
    edited May 11, 2011
    If you have access to another camera body do try the same test on that body to see if the behavior is related to the camera's AF technology itself.

    As I said, my copy of the lens (on any body) is not reliable at close focus distances but it's very reliable at distances of ~12 feet or greater, which is where I use it. I regard the benefits to be worth the effort and expense.
    ziggy53
    Moderator of the Cameras and Accessories forums
  • Manfr3dManfr3d Registered Users Posts: 2,008 Major grins
    edited May 11, 2011
    Thanks for the quick replies. I will try another camera and see how it goes.
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
  • SamSam Registered Users Posts: 7,419 Major grins
    edited May 11, 2011
    After reading this I took my 135 out and tested it. I found a small amount of back focus and fixed that with micro adjustment.

    The auto focus seemed to work at both close and far subjects?

    Sam
    www.samlinvillephotography.com
  • ziggy53ziggy53 Super Moderators Posts: 24,129 moderator
    edited May 11, 2011
    Sam wrote: »
    After reading this I took my 135 out and tested it. I found a small amount of back focus and fixed that with micro adjustment.

    The auto focus seemed to work at both close and far subjects?

    Sam

    Mine does not AF properly at close distance on either a 1D MKII, 40D or 5D MKII. Give it a little room and it works splendidly on all.

    For anything close I just manual focus. Not a biggee since I don't really want to use that lens for close focus.
    ziggy53
    Moderator of the Cameras and Accessories forums
  • Manfr3dManfr3d Registered Users Posts: 2,008 Major grins
    edited May 21, 2011
    Update:

    Same problem on another camera body but focus is perfect for anything
    further away than about 8m. Guess I'm gonna keep this lens with prices
    going up and everything. I begining to really like it as a lens for streetshooting
    too. Thanks for taking time to check your lenses and giving advice. Much
    appreciated!
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
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