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Thread: Odd Focus Plane

  1. #1
    Super Moderator Kayaker72's Avatar
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    Odd Focus Plane

    I've been noticing what I think in an odd focus plane in the occasional photo that last 4 months. I was wondering if someone knew what was going on.

    Here is an example from Sedona AZ:

    Slightly cropped image:

    small-9260 by kayaker72, on Flickr

    Left of center (what I consider to be sharp):

    small-9260-3 by kayaker72, on Flickr

    Right of center (what I am concerned about):

    small-9260-2 by kayaker72, on Flickr

    This is happening infrequently, but I have probably seen it ~10 times in the last 4 months. All shots were taken with the EFS 15-85 on the 7D. This particular shot was @24 mm, 1/200, f/4.5, ISO 100. I know that f/4.5 could produce a limited DOF if I focused within ~30 ft, but it is more that the focal plane seems angled that concerns me. Is it normal and I just haven't noticed it before? A loose element? Any thoughts?

    Thanks,
    Brant

  2. #2
    Member Poik's Avatar
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    What seems odd to me is in the slightly cropped image the dirt and plants on the right in the foreground seem to be perfectly in focus, whereas the stuff in the left that looks to be the same distance away from the camera is not in focus at all. So, top left and bottom right are in focus, and top right and bottom left are out? Just an observation, I don't know enough about optics to give any meaningful guestimates of what is going on.
    - Eric
    Canon 7D, 70-200 f/2.8 II, 17-55 f/2.8, 10-22mm f/3.5-4.5, 100mm f/2.8 Macro, 50mm f/1.8 II, 28-135mm f/3.5-5.6, 2x III, 430EX II
    flickr.com/ericolsson

  3. #3
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    Maybe something in the air, like hot air turbulences?
    The tree to the right of the center is also closer than the trees on the left, so that could be outside the DOF.

    I think this will be difficult to blame on the lens without test charts ...
    I sit always the right side that is OOF?
    Arnt

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    Yeah, I noticed that too, sharp bottom left/top right, and blurry bottom left.
    That's what you get when you use a Tilt lens like a TS-E.
    But it's also what you get when a single element is tilted, or 'decentred'.
    Here is a nice write up on the phenomenon.
    And you're right, it can happen with a loose element or three. From what I've heard the 15-85 is a bit prone to it, my copy vignettes differently on the left-right sides at 15mm, which is also a sign of decentring. Does yours? Other than that, have you dropped it, or even slightly banged it lately? even worse if the IS was on at the time? and did you use IS for the shot? sometimes the IS elements might not settle to the correct spot when you turn it off.
    Another thing to look out for is a worn mount on the lens or the camera, a tiny bit of wear at wide angles can lead to a lot of 'tilt' too.
    An awful lot of electrons were terribly inconvenienced in the making of this post.
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  5. #5
    Moderator Steve U's Avatar
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    This shot while it does show something, probably isn't the best for narrowing down any faults. Have you tried shooting in portrait configuration, then turning the camera 180 degrees and reshooting to see if the fault can be duplicated, top and bottom of image?

    Some more test shots needed.
    Steve U
    Wine, Food and Photography Student and Connoisseur

  6. #6
    Super Moderator Kayaker72's Avatar
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    Quote Originally Posted by Dr Croubie View Post
    Yeah, I noticed that too, sharp bottom left/top right, and blurry bottom left.
    That's what you get when you use a Tilt lens like a TS-E.
    But it's also what you get when a single element is tilted, or 'decentred'.
    Here is a nice write up on the phenomenon.
    And you're right, it can happen with a loose element or three. From what I've heard the 15-85 is a bit prone to it, my copy vignettes differently on the left-right sides at 15mm, which is also a sign of decentring. Does yours? Other than that, have you dropped it, or even slightly banged it lately? even worse if the IS was on at the time? and did you use IS for the shot? sometimes the IS elements might not settle to the correct spot when you turn it off.
    Another thing to look out for is a worn mount on the lens or the camera, a tiny bit of wear at wide angles can lead to a lot of 'tilt' too.
    Dr....I don't have a TS-E, but agree, that is what I am seeing too. Thanks for the link, I'll work on setting up the tests later today.

    As for your questions, have always seen more vigetting in the top left corner and to a lesser extent the bottom left. The lens hasn't been dropped recently, to my knowledge. IS was on at the time, I almost always shoot with IS on for the 15-85. I did check for wear, but don't see anything obvious.

    Quote Originally Posted by Steve U View Post
    This shot while it does show something, probably isn't the best for narrowing down any faults. Have you tried shooting in portrait configuration, then turning the camera 180 degrees and reshooting to see if the fault can be duplicated, top and bottom of image?

    Some more test shots needed.
    Thanks Steve....I'll give that a try as well. I've only noticed the issue in landscape and not in any of my portrait shots, so it will be interesting to see if it can be replicated.

    The phenomena is not consistent at all. For example from the day in Sedona, I only see the issue in 2-3 of over 240 shots. So, an issue with IS or a loose element makes sense to me. A few other examples from that day that were perfectly sharp (to my eye):


    Sedona-9428 by kayaker72, on Flickr


    Sedona-9268 by kayaker72, on Flickr

    Granted, the rest of the day I shot at f/5.6-f/11. I apparently hadn't had enough coffee yet when I took the landscape shot at f/4.5


    Thanks for the suggestions....
    Brant
    Last edited by Kayaker72; 01-19-2013 at 12:58 PM.

  7. #7
    Super Moderator Kayaker72's Avatar
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    In processing the photos from last night, I could see the issue fairly repeatedly. At this point, I am planning on sending the lens into Canon for repair unless someone has another idea of how to fix it.

    Full image:

    Boston-1402 by kayaker72, on Flickr

    Left side of the frame:

    small (1 of 1) by kayaker72, on Flickr

    Right side of the frame:

    small (1 of 1)-2 by kayaker72, on Flickr

    Thanks everyone for your help....
    Brant

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