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ANGENIEUX 16-44mm "VARIABLE PRIME" LENS REPAIR


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#1 Robert Hart

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Posted 13 April 2017 - 02:22 PM

I am restoring a complete clean lens of this type from two damaged examples. Before I go to the torment of designing and building a PL or direct IMS mount for this lens, does anyone have a clue on where to find a machine design diagram for a PL mount for this lens?

The two specimens I have wear the Cameflex and Aaton mounts. I can calculate and draw my own design but machining a new mount will be easier from a proper design.

My intention was to take the easy way out and machine up an ARRI standard tail, attach a PL-Mount adaptor and use shims to get the collimation right. Making the PL-Mount is somewhat of a challenge.

I have made them for other lenses and the similar IMS-Mount for a Speedbooster adaptation  to the SI2K camera IMS-Mount. Small hobby lathes struggle a bit with the wider diameter of the PL-Mount. 

Any advice will be greatly appreciated.

 


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#2 Dom Jaeger

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Posted 13 April 2017 - 03:59 PM

Hi Robert,

Yes I think it would certainly be easier to machine a Standard mount rather than a PL and then use an adapter, although decent S to PL adapters can be several hundred dollars.

I don't know how professional you want your lens to be, but original PL mounts are steel. Aluminium or chromed brass can wear or deform and throw out the crucial back- focus. But for hobby or occasional use it's not so vital.

I've not found an official source for PL mount dimensions, just measured one carefully for someone who wanted to machine an adapter. There are variations among manufacturers regarding certain dimensions, like depth of the rear throat or flange cut-out shape. The important ones are flange thickness (2.00mm - 0.02), throat OD (from memory 42.00 - 0.02, anyway needs to be a very snug fit in the PL cavity), and flatness (within 0.02). Those are my estimated tolerances.

Good luck with the project!
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#3 Peter Welander

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Posted 13 April 2017 - 04:49 PM

Do you have official dimensions for an Arri standard mount? Certainly one can reverse engineer the relevant diameters, but I'm interested in how the slot on the back is positioned to engage with the key on the camera.

 

Thanks.


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#4 Dom Jaeger

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Posted 13 April 2017 - 05:28 PM

I don't have official dimensions sorry. Maybe buried somewhere at my old workplace, but I'm not there anymore.

The slot position is pretty crucial when mounting to a camera but most adapters either use grub screws or a lock ring that screws up against a clip-on ring that locates in that groove, so in those cases the position doesn't matter so much.
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#5 Robert Hart

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Posted 14 April 2017 - 02:38 AM

Peter. I think the ARRI mount you refer to is the ARRI "B" or bayonet development of the original ARRI standard mount. From recall and checking the Wiki on the mount, the flange to focal plane is the same as PL at 52mm with a shoulder diameter of 41mm. The distance along the should from flange face to front and rear of key and from flange face to circlip channel I would have to measure. The original ARRI standard mount design was dreadfully imagined with the lens free to turn inside the mount.

I can only assume that the original reasoning for the free-turning mount and the "ears" on the lens barrel may have been that by turning the actual lens body and holding the front focus ring to refocus, that any optical defects in the image would not turn with focus adjustments. The image shift during focus pulls must have been horrendous.

A couple of old fungus-rescue Cooke Series 2's with aluminium mounts have considerable wear on the mount shoulders.

Different lens manufacturers seem to have evolved their own methods of creating the bayonet key in their ARRI B mount tails. One example I have seen was setting an entire key shape into a woodruff key style slot with the outer piece cut to the ARRI profile and secured with small screws. Because of often small workspaces within a design, that option mat not always be available.

Another style seems to have used a swageing technique to deform the key outwards from the base material and machine that to final shape. Another seemed to have turned and milled the entire key from the base material.

An old fungussed Angenieux 25-250mm I repaired had been modified by somebody back to the original ARRI standard shape so I no longer have a reference to measure for you for the ARRI B.

I added a chinese PL-Mount adaptor to that one and hit lucky gold in that it required no re-collimation to zoom true. Keeping the fungus under control is another matter.


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#6 Peter Welander

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Posted 14 April 2017 - 06:38 AM

One of the things I have tried to imagine is a way to get various lens options for 35mm cameras, thinking particularly of something like a 35BL1 and the like, for those of us who find PL offerings largely too costly. I find the notion of changeable mount lenses such as the Rokinon Xeen intriguing. Naturally it is available with a PL mount option, but think of how many users of IIc and other similar cameras could benefit from either an Arri Standard or Arri Bayonet option. The former would be easier to make, hence my interest, but even the bayonet is not beyond the capability of a decent machinist.

 

I've never seen one of the really early Arri Standard lenses that rotates in the mount. I agree that the concept is "dreadfully imagined." I don't want to carry a jar of Vaseline in my bag, or is that just legend?


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