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Thread: shimming adapters NEX

  1. #1
    mike_hk2ksk
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    shimming adapters NEX

    I recently underwent shimming exercise with 2 of my 3 NEX adapters. Rayqual-made Pentax adapter was dead on and didnít require any adjustments. Both Leica-M and Nikon RF adapters required shimming by 8 to 10 mils (0.25 mm) to achieve spot-on infinity focus. Immediate side benefit I noticed was significantly improved MFD, by as much as 20 Ė 30 cm. But I think I am also seeing quite noticeable increase in corner-to-corner sharpness and overall picture quality even with wide-open fast lenses. What is your expert opinion please: by fine-tuning FFD by roughly 1%, is it reasonable to expect this improvement in picture fidelity? Thanks in advance.

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    Senior Member douglasf13's Avatar
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    Re: shimming adapters NEX

    I wouldn't imagine that shimming the adapters would improve image quality at all, outside of the minimum focus distance as you mentioned.

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    Re: shimming adapters NEX

    Quote Originally Posted by mike_hk2ksk View Post
    Both Leica-M and Nikon RF adapters required shimming by 8 to 10 mils (0.25 mm) to achieve spot-on infinity focus.
    Who is manufacturer of Leica-M and Ninon RF adapters that required shimming?

  4. #4
    mike_hk2ksk
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    Re: shimming adapters NEX

    Quote Originally Posted by douglasf13 View Post
    I wouldn't imagine that shimming the adapters would improve image quality at all, outside of the minimum focus distance as you mentioned.
    So Douglas, what you are saying is: accuracy of a lens placement in the camera with respect to its designed Flange Distance has no effect on the image quality? What if the lens was off by 10% not 1% as in my case, would that introduce a considerable distortion? Thank again for your comments.

    Both adapters are CV-made.

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    Re: shimming adapters NEX

    Quote Originally Posted by mike_hk2ksk View Post
    Both adapters are CV-made.
    Wow, interesting. As I am using CV adapters could you please let me know how you found out exact amount they are off?

  6. #6
    mike_hk2ksk
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    Re: shimming adapters NEX

    Quote Originally Posted by ZoranC View Post
    Wow, interesting. As I am using CV adapters could you please let me know how you found out exact amount they are off?
    My VM adapter reached infinity focus @ around 5m mark, way off. SC-adapter was better - infinity @ 20 m but I decided to improve both adapters. I used many layers of heavy aluminum foil, 1 mil thinkness and exprimented with shim thikness by shooting far-off objects and the moon, as a guy from the other forum recommended. I over-shimmed initially , then removed a few layers and now all lenses reach infinity focus spot-on. There is some variation on Nokton 35/1.4. At f4 and to a lesser degree @ 5.6 infinity focus is off just a little. This I beleive is a well described focus-shift issue - can't be helped. All other lenses (5 in total) are great. Here is a 400% crop of the shot with focus set @ the infinity mark with a shimmed adapter. Considering this is 4x magnification - I am happy.

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    Senior Member douglasf13's Avatar
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    Re: shimming adapters NEX

    Quote Originally Posted by mike_hk2ksk View Post
    So Douglas, what you are saying is: accuracy of a lens placement in the camera with respect to its designed Flange Distance has no effect on the image quality? What if the lens was off by 10% not 1% as in my case, would that introduce a considerable distortion? Thank again for your comments.

    Both adapters are CV-made.
    It don't believe that it should make a difference, as long as focus is possible. Many use extension tubes for macro shooting that add considerable flange distance.

    There seems to be a lot of variation between lens design and adapter thickness, and that makes it hard to nail down why/what is causing the seemingly wide discrepancy tolerances.

    For example, both my Metabones and Voigtlander M adapters behave similarly with my Voigtlander 35/1.4. At f1.4, both adapters focus slightly past infinity. At f8, they focus WAY past infinity. However, with my MS Optical 35/3.5, my Voigtlander M adapter looks to be dead on at infinity. So, now I'm wondering if it isn't the adapter at all, but rather my lens.

    Have you tested multiple lenses at various apertures at infinity?

  8. #8
    mike_hk2ksk
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    Re: shimming adapters NEX

    Quote Originally Posted by douglasf13 View Post
    Have you tested multiple lenses at various apertures at infinity?
    Yes I tested 4 S/SC lenses and 2 M lenses in one stop incerements through f8/f11. Results were consistent across aperture settings and from one lens to another.

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    Re: shimming adapters NEX

    Quote Originally Posted by mike_hk2ksk View Post
    So Douglas, what you are saying is: accuracy of a lens placement in the camera with respect to its designed Flange Distance has no effect on the image quality? What if the lens was off by 10% not 1% as in my case, would that introduce a considerable distortion? Thank again for your comments.

    Both adapters are CV-made.
    shouldn't make a difference, the adapter being off is the same as the lens being focused off by that same distance. most lenses focus by moving all lens elements together, thus adapter size variation only effects where the focus ring is for a given distance to be in focus, not the image quality at that focus distance. there are two cases where this is not true however: 1) when the the adapter is lopsided (rare) introducing tilt or 2) if the lens has a floating element - this means that not all lens elements move together during focusing (typically it is more modern and more expensive lenses that have floating elements). if your lenses have floating elements that would probably explain the iq improvement, otherwise it is very surprising.

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