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Micro Adjusting Lenses

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  • 19-07-2016 11:35pm
    #1
    Pulse8
    Registered Users Posts: 550 ✭✭✭


    Hey guys, I shoot with a Canon 7Dmkii

    Have read a fair amount online about micro adjusting lenses although the whole printing of charts & taking numerous pics really didn't appeal to me but the niggling feeling that my Sigma 10mm Fisheye needed to be adjusted kept at me.

    Then I found this really really simple guide to it but I'm not sure if what the guy was saying was correct.

    Basically he said to place camera on a tripod, switch to live view....zoom in on screen & focus on your point till it looks perfectly sharp on screen.

    Then switch to viewfinder & one shot mode using the centre AF point, making sure that AF point is on the same point you focused on during the live view portion.

    Half press your shutter button to focus through the viewfinder if your focus ring moves at all then you're indeed either back or front focusing?

    I messed around with the adjustments so now that my focus ring doesnt alter when I switch from having it tack sharp in live mode to focusing through the viewfinder....just wondering if this is indeed a legit method?

    As before I altered the adjustment settings the focus in viewfinder mode would do its thing, I'd then switch the lens to manual focus & the camera back to live mode to see how it looked & it would be slightly off thus proving that by moving it was knocking itself off


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    #2
    Whammy!
    Registered Users Posts: 285 ✭✭Whammy!


    That's pretty much it. Albeit a little over simplified.

    Here is a link from Canon explaining the steps.
    http://www.learn.usa.canon.com/app/pdfs/quickguides/CDLC_Accurate_EOS_AF_QuickGuide.pdf

    Ideally you should be comparing the live view photo and the auto focused photos on your computer screen, zooming in 100%.
    When testing an adjustment setting you should take at least 3 auto focused photos at that setting. This is to eliminate the chance of a lucky pin sharp focus, which can happen.

    You should also take the photos under good light on a high contrast subject to making auto-focusing easier.

    Also the distance you are from the subject makes a difference.
    The camera to subject distance should be no less than 50 times the focal length of the lens. So for a 50mm lens that minimum distance would be 2.5 meters.


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