Lens calibration

Discussion in 'Canon EOS Digital SLRs' started by Pete.c, Jun 9, 2021.

  1. Pete.c

    Pete.c Member

    Joined:
    Oct 13, 2018
    Messages:
    61
    Equipment:
    Canon Eos 5D iv, Canon EOS 77D, Canon 10 - 18mm, Sigma 17-70mm, Sigma 105mm macro, Sigma 70 - 300mm, Tamron 150-600mm F/5-6.3, Canon 50mm 1.8 STM
    Hi all, Quick question!

    I'm sure many of you have calibrated your own equipment. I have noticed my one of my lenses is back focusing. I have watched many YouTube videos regarding this subject and some say 6ft from the target for a 600mm lens as that distance will cover all lenses. And others say a minimum of 40ft. What would you recommend .

    Pete
     

  2. johnsey

    johnsey Site Moderator Staff Member Site Supporter

    Joined:
    Apr 21, 2017
    Messages:
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    Location:
    Fargo, ND
    Equipment:
    5dMk4, 5dMk2, 20D, 70-200 2.8L IS, 100mm 2.8 Macro USM, 50mm 1.4, 85mm 1.8, 17-40mm 4.0L, Rokinon 14mm 2.8; Pixma Pro-100
    You want to be on the close side where you will have shallow depth of field wide open. You need the focus to fall off to softness right away to see the AF issues, 6ft sounds about right at 50mm but you may need to step closer or back up depending on how wide or long your lens is.

    https://photographylife.com/how-to-quickly-test-your-dslr-for-autofocus-issues
    I have never had to adjust my lenses, and I would say if its very close and a micro adjustment in camera does the trick then by all means do it. Ideally you want to identify right away and send back to the manufacture for replacement. There are lenses that get shipped out brand new out of adjustment. They sample them at the factory and have a small range of acceptable performance results, but not every lens is tested to make sure it is perfect.
     
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  3. Pete.c

    Pete.c Member

    Joined:
    Oct 13, 2018
    Messages:
    61
    Equipment:
    Canon Eos 5D iv, Canon EOS 77D, Canon 10 - 18mm, Sigma 17-70mm, Sigma 105mm macro, Sigma 70 - 300mm, Tamron 150-600mm F/5-6.3, Canon 50mm 1.8 STM
    Just discovered the back focusing by accident, I shot some pictures I know we're definitely on the eye, which turned out very soft. But just above the birds head it was tack sharp. I tested this several times and the results were the same. So I'm going to try a little micro focusing. I understand that when the lens leaves the factory there will be a little tolerance, so it ma be just off a little. Just wanted to get the distance right.
    The lens is a 150 - 600mm f5.6 - f6.3
     
  4. johnsey

    johnsey Site Moderator Staff Member Site Supporter

    Joined:
    Apr 21, 2017
    Messages:
    1,158
    Location:
    Fargo, ND
    Equipment:
    5dMk4, 5dMk2, 20D, 70-200 2.8L IS, 100mm 2.8 Macro USM, 50mm 1.4, 85mm 1.8, 17-40mm 4.0L, Rokinon 14mm 2.8; Pixma Pro-100
    I would suggest a test in a controlled environment outlined like the one in the link above, focusing on a focus chart on a flat wall wide open optimize the test to confirm if it is lens or something else.
     

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