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Thread: Zeiss zooms AF inaccuracies

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    Senior Member edwardkaraa's Avatar
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    Zeiss zooms AF inaccuracies

    I have been using both zooms for several months and have consistently noticed AF inaccuracies. Here are my observations:

    24-70: At close distance from MFD to around 4-5 meters, focus is right on, however at infinity there is an evident front focusing that requires an AF adjustment of +5 for sharpest results. The problem is that the close distance focusing is no longer accurate as it back focuses. The lens seems to be calibrated for closer distances.

    16-35: Seems to be calibrated for infinity, where it is spot on. At closer distances, it back focuses, which brings me to exactly the same problem, as when I adjust AF to get sharpest results at close distances, it front focuses at infinity

    I am not sure if this camera related, but all other lenses focus perfectly. I suspect that Sony has calibrated the lenses for best results taking in consideration the field curvature, but I'm not really sure about that.

    The fact remains, both zooms seem to be unable to AF accurately at either close or far distance. Adjusting one will screw up the other.

    I wonder if any of you guys has experienced the same.
    M262 ZM 25/2.8 35/1.4 50/2 85/2

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    Super Duper
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    Re: Zeiss zooms AF inaccuracies

    Quote Originally Posted by edwardkaraa View Post
    I have been using both zooms for several months and have consistently noticed AF inaccuracies. Here are my observations:

    24-70: At close distance from MFD to around 4-5 meters, focus is right on, however at infinity there is an evident front focusing that requires an AF adjustment of +5 for sharpest results. The problem is that the close distance focusing is no longer accurate as it back focuses. The lens seems to be calibrated for closer distances.

    16-35: Seems to be calibrated for infinity, where it is spot on. At closer distances, it back focuses, which brings me to exactly the same problem, as when I adjust AF to get sharpest results at close distances, it front focuses at infinity

    I am not sure if this camera related, but all other lenses focus perfectly. I suspect that Sony has calibrated the lenses for best results taking in consideration the field curvature, but I'm not really sure about that.

    The fact remains, both zooms seem to be unable to AF accurately at either close or far distance. Adjusting one will screw up the other.

    I wonder if any of you guys has experienced the same.
    LOL, no one wants to post on this thread. Wonder why?

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    Re: Zeiss zooms AF inaccuracies

    In Zeiss zooms, I only have the 24-70 which I haven't used enough to know if there is a problem.

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    Senior Member douglasf13's Avatar
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    Re: Zeiss zooms AF inaccuracies

    I haven't noticed this, but now I'm afraid to test it! LOL

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    Senior Member ecsh's Avatar
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    Re: Zeiss zooms AF inaccuracies

    I have both, i will try them and see, that is, if it ever stops raining up here in the NE. I feel like a duck.
    Joe

  6. #6
    Shelby Lewis
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    Re: Zeiss zooms AF inaccuracies

    Edward... what you describe is something I've gone through with the sigma 50/1.4. Inside 10-feet, it's fantastic. Outside of 10', it's hit or miss. Consequently, my 135/1.8 is spot on no matter the distance. As a matter of fact.... it's scary how accurate it is.

    My sony 28/2.8 also seems to have a focus shift to the rear, but is something I need to test more in order to pin it down.

    Ah... the quest for lenses that do what they are good at, regardless of aperture or distance to subject, continues.

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    Re: Zeiss zooms AF inaccuracies

    My 24-70 needs a +6 adjustment at around 2-3 meters (6 to 10 ft) but I haven't checked it at infinity - partly because such shots are usually stopped down in my work. But I will have a look tomorrow.

    My other Sony lenses (70-300 G, 70-400 G, 500 mirror) tested spot on. Likewise my Sigma 70 macro and 12-24 mm, though the latter needs f11 to be sharp anyway!

    Bill

  8. #8
    lecram
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    Re: Zeiss zooms AF inaccuracies

    am I glad that I ran into this forum. I've been up and down other forums(the other two that start with D) and no one there has seen this. My 135/1.8 needs a +2, but my 28/2 needs a +15 when the subject is within 6 feet, anything outside of 6 feet with the 28/2 I still have not seen in focus results.
    The other strang issue is when using spot focus I've got to use the top of the square when trying to get the focus spot on.

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    Re: Zeiss zooms AF inaccuracies

    How are you guys testing? After reading this I should get serious and calibrate the lenses.

  10. #10
    lecram
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    Re: Zeiss zooms AF inaccuracies

    I would say hold off on doing any adjustment if your focus seems to be working as it should.
    I just so happen to be taking a picture with the 28mm @f2 so i can take advantage of that small DOF and noticed that what was in focus isn't what I was expecting to be in focus.
    If you want to test your setup try using the following chart available here:
    http://focustestchart.com/chart.html

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