Nikon Lenses on PL-big URSA 4Kv1.

I am examining how to use a fairly good set of fast but old Nikon lenses on a big URSA. Logically, I should use the EF version as EF-Nikon adaptors are common and affordable. However the URSA I have aquired is the PL-Mount version.

It is proving a bit difficult getting info from BM relating to the design differences between the PL and EF turrets. My understanding thus far has been that the two turrets are entirely different. On initial inspection, it appears that the same turret base may be used for both the big URSA EF and PL versions with the different mounts being accommodated via an adaptor ring.

I have made Nikon mounts using genuine Nikon F-Mount rings for AGUS35 adaptors and the SI2K. I can make one for the BM URSA but would prefer using genuine BM EF-Mount parts if they can be aquired. I can understand BM would want to keep their intellectual property close and prefer to do warranty or other repairs in-house.

My enquiry to others here is if anyone has taken their EF mount off the big URSA to add after-market anti-aliasing or contrast filters to the URSA throat. I would like to know if the mount ring and release is a single piece which fits into the turret base or is a two-piece assembly?

From my understanding the big Ursa turrets are an intergrated unit, the lens mount and sensor are fixed in a single assembly. The EF version is not removeable,due to the electrical contacts for the EF mount.

The Ursa Mini PL, (perhaps a similar FFD) lens mount is user removeable for the BM B4 mount accessory, but not the big Ursa. Making a dump EF or Nikon mount dormthe Mini PL camera was looked at by HotRod cameras, whomdo custom camera work, and it became a no go. I have a feeling the Ursa PL Turret is fixed to the PL FFD which is longer than Nikon, so if you did get a Nikon mount in place of the PL, you would not get inf. Focus.

Converting a Nikon lens to PL was looked at by Duclos, and again buying PL lenses like the Zeiss CPs would cost less than converting an old Nikon lens. So I would say, this is a non-starter idea. I also looked into this, and ended up selling my Nikon mount lenses, and getting PL lenses instead.
Cheers

In the big URSA, the PL-Mount itself is fastened by six small screws over another inner ring which is itself fastened with six separate screws on different centres. With the PL-Mount itself taken off, there remains a shallow workspace but enough to fit a spacer with a genuine Nikon F-Mount ring on it with shallower-headed attachment screws. The lock pin and release might be a challenge to design but doable.

If the inner ring is removed, then there is a lot of workspace to design a substantial Nikon-style mount within, even an Optitek or IMS style professional clamp ring arrangement similar in function to the PL-Mount clamp ring. For simplicity and to be honest, less effort and better precision, my choice would be to have an entire EF mount assembly to swap in and to use the EF-Nikon adaptors.

My imagining relating to the EF-Mount electrical connection is that the connection would be by some sort of feed-through conductors or ribbon cable from the circuit board within the turret. The base turret for the PL version may simply be missing an electrical sub-assembly for the Canon lens servo controls. I am interested only in the mechanical mount.

If it is not tapered behind the corrugated removable anti-reflection cone, the throat of the big URSA behind the lens mount may be amenable to fitment of a focal reducer optical set for concentrating a wider lens image onto the smaller 4K sensor. That is another adventure to contemplate some other time.

I replaced my set of Nikon primes with 2 tokina zoom lenses - the 16-28 and 50-135 pl t3 when i bought the URSA pl. They can be half the new cost used on eBay.

A bit of info for the curious. I can't make the image thing here work.

http://www.dvinfo.net/forum/blackmagic- ... ost1933428

This design exercise does not permit a lock pin and release for the Nikon mount.

Persons who have no facility or ability for fine and detailed workmanship should not interfere with their cameras and I do not encourage inspired amateurs to take the risk.

Bob, does this allow for,the proper FFD between the lens mount and sensor on the Ursa? PL FFD is longer than Nikon.
Cheers

QUOTE - "does this allow for the proper FFD between the lens mount and sensor on the Ursa? PL FFD is longer than Nikon".

Yes it does. I have manually offered the Nikon lenses in air up to the front of the camera. There is about 7.3mm of workspace in front of the existing inner BM adaptor to design within.

If you look at the diagram I have linked to, the tail of the new adaptor for the FM2 Nikon mount to fasten on to, slides inside the inner adaptor of the camera which remains undisturbed. This is not removed. It is secured inside the front of the camera body with its own short six screws. The Nikon adaptor will attach using the separate six screw attachments for the PL-Mount. The screws may have to be shorter.

In that diagram, additional clearance segments for the corrugated disk spring behind the Nikon mount are not illustrated.

My imagining is that BM's two-piece arrangement may be some sort of a future-proofing workaround by BM to enable a longterm PL-Mount design to be used. A PL-Mount is a complicated piece to make and costly to alter. A thick disk shim with screwholes is easier to resize or replace.

BM at some point may have designed in the option of some other lens types but this would have created the nightmare of custom ordering and too many separate related camera models instead of vendors having to maintain inventory of only two basic models.

I am surprised that third-party players have not designed and marketed their own alternative mounts and accessories like they did with RED. Then again, like RED, BM would be wisely protective of its intellectual property and registered designs.

Rushed accessories of third-party origin which themselves fail or cause failure or damage can complicate life for a camera manufacturer and impugn the reputation of a product purely by negative association.

A lean business model does not leave much room for the distraction of formally assessing and approving third party accessories. I have no idea how lean or fat BM is but the company has enough on its hands testing and approving third party recording media across several products, let alone other bits and pieces and policing QA on it all.

The main reason I think, is a lack of Ursa sales, this also doomed the Ursa Turret upgrade. So no real sale base for new mounts, HotRod Cameras had a similar nisduevwuth lack I'd real volume interest in the Ursa Mini mounts they looked into developing.
Cheers.

For the sake of curiosity only, here is a link to some diagrams of my Nikon F-Mount project for the BM URSA 4KV1. Please do not accept the dimensions shown as guaranteed accurate.

http://www.bmcuser.com/showthread.php?2 ... M4kPL-URSA

For furthur curiosity sake, here is a link to the assembled adaptor and Nikon F-Mount waiting for 10 screwholes to be drilled and 4 tapped for the Nikon screws.

http://www.bmcuser.com/attachment.php?a ... 1497795669

Congrats, on the progress so,far. Good luck with the project.
Cheers

Thanks for the good luck thoughts. I am right on the very thin edge of my abilities and means to do the job so luck certainly helps.

For what it is worth, the job is done. Marking out those six BM screwholes and drilling them to fine tolerance is a bit of a challenge. The heads of the allen-head screws have only 0.5mm shoulders and if you get too excited drilling the holes you could end up with a screw head that pulls down inside the hole of your newly made adaptor. It will need shimming forward just a fraction.

The bits and pieces were near-to spot on when offered up but with fasteners pulled down, the Nikon flange is now just a little too far rearwards. It is amazing what a difference those little screws make.

The allen-head screws need to be replaced with shallower and broader headed screws for a better finish and to allow clearance of the aperture control ring of manual Nikons. The screw heads are a "just fit" which makes the aperture ring on some lenses tight to move. The screws need to be a fraction shorter as well. The allen-head screw ends just touch bottom in their holes in the camera body as they snug down on the adaptor.

The move to a five hole fixture on the URSA Mini cams appears to be driven by the need to provide workspace for the Canon ( and Nikon ) lens lock pin release mechanism. The six hole pattern places a screw directly in the position occupied by the lens lock pin release mechanism.

My personal preference would have been to make Canon and Nikon lens mounts in the IMS professional or Optitek ProLok style but those would introduce added cost and defeat the competitive edge price-wise that the BM cams have.

FWIW, here is a link to a clip of Nikon images on the big URSA via the custom mount just to prove I didn't wreck anything. It was a dull late rainy afternoon and the route of the image was playback in camera via HD-SDI to a recorder, then export from Premiere CS6 to .wmv. The images are looking rather soggy but appear much sharper on a TV direct from camera playback.

I hope to get something much more colourful on a bright day at a slower ISO

http :// www . youtube.com/watch?v=tId-fPKc1zo&feature = youtube

You'll have to copy/paste to a new address bar and delete the extra spaces in the web address. For some strange reason, youtube tried to embed the clip in this message and it becomes all munted.

This is cool Robert! Here is the direct link to your video:

Maybe you can post some pictures of the lens mount with lenses attached?

Ryan.

Thanks for making that link embed thing work.

Here is a link to a discussion which if you scroll down includes a pic of the complete assembly including attached lens. The sending of an image to this page is a high science I still have not yet worked out.

http://www.bmcuser.com/showthread.php?2 ... URSA/page2

Now if only BM could make the 4.6K turret available from any limited residual stock, even if it was crippled down in frame rate to 25P and no global shutter, I would be in pig-heaven. Alas if wishes were horses ...

Here is a bit more test footage from the "big" URSA and Nikon AIS lenses.