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    I have a comprehensive set of fast AIS Nikons, which I can't hope to replace cost-wise. Time to get started and draw the proper design and devise the method for least waste of metal stock. The little guys in Dongguan could probably dream about it the night before, design it, make it, hard-chrome finish it and package it before I can and sell it for less than the cost of the metal stock too. - So onward to hunching over the machine and looking like Quasimodo by the end of it all.

    There is probably the "doing it because I can, not necessarily because I should" factor at play here as well. BMUNIKON01.jpg
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  2. #2  
    Senior Member
    Join Date
    Feb 2013
    NIKKOR AI/AIS can easily be adapter to Canon EF mount. Especially since they have aperture control built into the lens. You're set.
    Steve Lee Jean
    Busan, South Korea + Los Angeles, CA
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  3. #3  
    The camera is the PL-Mount big URSA, not the EF-Mount version. If it was the EF-Mount version then I would be having an easier time with a simple adaptor, or a few because they are cheap enough.
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  4. #4  
    Senior Member
    Join Date
    Sep 2012
    The only way it would be remotely possible is by cutting off the PL mount and fabricating a new mount, an adapter won't work. Cheaper, faster, and easier to sell the PL version and buy an EF model. If you've just wan't to get busy why not do something with a future like designing an F mount for the mini?
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  5. #5  
    An adaptor can and will be done. The PL-Mount attaches through a separate ring which is itself a supported spacer within a receiver machined into the camera turret front body. No cutting of the PL-Mount is necessary. The existing allen screws which attach the PL-Mount have heads which may protrude beyond the front of the adaptor and interfere with the rear body of some Nikon mount lenses. They may need to be replaced with shorter shallow head screws.BMURSA4KV1NIKONSPACERMOUNT.jpg
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  6. #6  
    Furthur to above, there is half a chance that this adaptor may work with the URSA 4K Mini PL. I have not had a chance to study one up close. However in on-line images I have looked at, the layout appears similar. It appears to be integrated into the camera body, not a separate turret module. If the locating shoulder on the rear of the Nikon adaptor can be made deeper, a substantial release pin mechanism should be possible and relatively simple, a hardened pin pressed into a wider hollow slide with spring inside. The pin would have to be ball-ended so that turning the lens firmly can force it in to release the lens. There does not appear to be sufficient workroom to arrange a release button. There may be enough workspace to design an Optitek-style Pro-lock locking mount which should not require rear workspace. There is however insufficient workspace to install an iris actuator for fully auto Nikon lenses but better imaginations than mine may be able to concoct one. My lenses are all manual lenses.
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  7. #7  
    For the sake of curiosity only. I make no assurances or guarantees as to accuracy of dimensions.BMURSA4KV1NIKONFCONCEPTUAL.jpgBMURSA4KV1NIKONSPACERMOUNT2.jpg
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  8. #8  
    Since studying the BM big URSA PL-Mount arrangement, I have read the URSA Mini manual and have found that whilst general principles are similar, the design differs significantly in that the PL-Mount on the Mini is attached with five screws, not the six found on the big URSA. The PL-Mount on the Mini also includes electrical connection for the intelligent lenses from Cooke. Given that inexpensive Canon EF-Mount to Nikon F-Mount adaptors can be found, changing the mount to the EF-Mount is the most convenient means of being able to use Nikon lenses. There would be little point to making a custom Nikon mount for the URSA Mini cameras. It could be done and perhaps a little more conveniently than for the big URSA PL because of the standardised shim system and availability of thick shims which could be stacked and longer screws used for the Nikon custom mount.
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  9. #9  
    It appears that for the big URSA at least, there is enough real estate to allow the older Canon FD mount lenses to be used via a custom inner adaptor spacer/mount which would be really simple to build in its basic form however may need added pieces to enable the manual aperture setting of the lens. I only had an old FD lens with mechanical auto iris linkage to offer up to the big URSA camera whilst the PL-Mount was off it. It achieves very close if not actual infinity focus held with the lock ring directly against the inner PL-Mount adaptor spacer. How to manually control the aperture on the FD lenses is another matter. There are clips on youtube which illustrate how it can be done.

    There "appears" from illustrations in the .pdf manual for the URSA mini there may be also sufficient real estate on the URSA Mini cams for a custom FD dumb mount to be made for the lens to mount directly, not via an optical offset Canon EF-FD adaptor.

    There being Canon EF-FD adaptors which contain an optical element to reposition the image plane of the FD lenses furthur rearward, a custom FD mount is probably pointless unless there are resolution losses via the added optical element in the EF-FD adaptor.

    If making any sort of non-genuine mount for the URSA Mini cams, EXTREME care would need to be taken NOT to make metal contact with any of the electrical conductors for lens control which reside inside the URSA Mini lens throat.
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  10. #10  
    Senior Member
    Join Date
    Mar 2015
    USA N. CA
    Ilya ar HotRod cameras had also determined a dumb EF mount for the Ursa Mini PL was possible spacevwise, but he ran into issues trying to get a test sample made, and due to a lack I'd interest outside the 13 or so responses, abonded tge project as it was not cost effective to do. Now with the Ursa discontinued and the Ursa Min Pro released, which has Canon EF, Nikon, PL and B4 mounts available, it became a non starter from a business POV. The BM Nikon mount for the UM Pro is a very nice, solid piece of kit from the few reviews of it, with one if the best Iris controls.
    Last edited by Denny Smith; 06-18-2017 at 11:48 AM.
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