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Nikon 55mm Macro Speedbooster BMPCC incompatible?

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  • Nikon 55mm Macro Speedbooster BMPCC incompatible?

    I recently bought a Nikon 55mm 2.8 Macro (great lens btw) but it seems hard to fit on the BMPCC Speedbooster. I am assuming this is due to the protruding rear element. All the other primes I own go much easier on the Speedbooster. However, carefully putting it on I cant seem to see where it is interfering. I haven't been using it as a result, because I did not want to damage anything.

    Has anyone else encountered this issue? Its not listed as a known incompatibility on the Speedbooster Website.

    Looked on Google & the forum search but couldn't find anything - apologies if this has been discussed before.

  • #2
    The 55/2.8 AiS Nikkor was one of several dozen Nikon lenses that I measured prior to finalizing the Speed Booster design. It *should* work. I would double-check it myself, but I don't currently have access to the lens.

    Since this lens has two groups that both move away from the image plane during focusing, you might want to try setting the lens away from infinity focus. That will ensure that glass-to-glass contact can't occur. If you still have problems connecting the lens and Speed Booster then it may be that there is a tolerance buildup issue on the lens mounts. Metabones adapters are intentionally made a little tight to minimize lens movement during focusing, so if you're 55/2.8 lens also has a slightly tight mount then you could encounter a very snug fit. I'm suspecting that this is the case since your other primes fit OK.


    • #3
      Wow, a reply from Brian Caldwell personally - didn't see that coming. Thanks for taking the time to respond.

      I tried again, even at close focus the glass is definitely not touching, so no issue there. At room temperature it seemed to fit better, even though it was still a little more snug than the other Nikons I own. I think the last time I tried to fit the 55mm I had just gotten the lens case and the camera from the car, so everything was quite cold.

      All in all, on further inspection, I am not really worried. I was just surprised that this lens feels tighter than the others. So there might different tolerances of the lenses that the temperature further exacerbated. And then there is the element of me being very careful (maybe overly so) around all things glass.


      • #4
        If it is an older lens, there are some subtle differences which cause baulky fitting on the modern Nikon F-Mount. There may be three causes from memory.

        Overhang of extensions on the aperture ring binding onto the rear face of a shoulder machined in the face of the Nikon F-Mount ring.

        Overhang of the same aperture ring binding onto the entire rear face of a shoulder machined in the face of the Nikon F-Mount ring.

        Inner diameter of this overhang fouling the diameter of the shoulder machined in the face of the Nikon F-Mount ring.

        A slightly longer or shorter distance between the flange face on the rear of the lens and the front face of the bayonet lugs. One or another of the lens series will either mount sloppy or bind on the lugs without turning the full angle of rotation to pin-lock. I have forgotten which. It was a vexing issue on the very early versions of the P+S Technik IMS NIkon F Professional mount until a design revision fixed it. Some of the 35mm groundglass adaptors ran into the same issue.

        From vague memory and please not not trust this, the older four-screw F-Mount rings as found on the Nikon FM2 I remember as having a shoulder which was 1.7mm deep rearwards of the flange face and a trace narrower along the shoulder diameter than the newer F-Mounts on which the depth of the shoulder was about 0.7mm.

        I have three lenses which would bind, a 55mm f3.5 Micro-Nikkor, a 55mm f1.2 and an old 85mm f1.8.

        To get the mount of the lens properly revised to match your other lenses and incur less risk of damage to the mount, you should seek advice from a lens technician. I think Brian Caldwell may well run with this comment and prove or refute it regarding the Speedbooster version of the Nikon F-Mount.

        I hope this helps and does not hinder.