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ISO Arri-B to PL adapter

Steve Cutler

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Hi Steve, my own opinion is to avoid those cheap $25-50.00 aluminum adapters. I have yet to find an accurate one.

Fotodiox makes a respectable adapter, but they vary in accuracy by up to +/- .03mm. This means you must shim the lens to the adapter in the case of high speed lenses. I quality control them using gage blocks & a precision height gage on a granite surface plate. I send back the ones that are more than .01mm out. 

Right now, I have a dead-on Les Bosher stainless B to PL quick-release adapter ($ 285.00 + shipping) and a QC'd Fotodiox unit that is also dead-nuts zero ($ 195.00). PL rear caps: $ 18.00.  Let me know if these interest you. 

Thanks !

Edited by Charles Pickel
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I second what Charles says about the cheap adapters, not only are they unlikely to be accurate, and use aluminium alloys rather than steel, but the grub screw attachment method is really not a good idea. If you overtighten them, it can deform the B mount underneath and cause focus binding issues, but if you do them up too loosely they can slip and lose back focus.

The Fotodiox ones use a much better system of attachment, but as Charles points out, the relatively low cost tends to compromise the accuracy. Better made versions of the same design by Visual Products and others tend to cost closer to US$400. 

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7 hours ago, Steve Cutler said:
Hi all, searching for an Arri-B to PL adapter (for S16 superspeeds....

Are they MK I, II or III..? If they are eight hole mounts (II or III), Frank at Slomo Digital in LA was selling some stainless PL mounts not that long ago. They were quite cheap but didn't come with the black rear light baffle.

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Good point Gregg, yes you could just replace the B mount if they have the 8 hole screw spacing.

I don’t know about the Slomo ones (didn’t you find some dimensional issues with yours Greg?) but Visual Products and P&S Technik both sell compatible PL mounts:



Get a technician to fit and accurately shim them.

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@Dom Jaeger

Slomo may not have any more so it might be moot. They were about 1/4 the VP or PSTechnik price. The clearance to allow shimming was there and the other dimensions seemed good. The fit into a PL lens port felt a bit snug to me, but I only had one port here to try, and I'm not used to PL.  I polished a few microns off in a lathe and it's now about 5 microns bigger than the Zeiss one I have. 

Unfortunately my micrometer couldn't quite fit. I did a comparative measurement by removing the anvil. That cylinder is supposed to be 54 -(0.025-0.075)mm. Those specs might have come from you Dom..

I think there is a fraction of a mm radius in the corner where the Zeiss one has a pronounced undercut about 1mm wide. So they may not satisfy your criteria. I could  probably send you one to look at if you're curious.


Edited by Gregg MacPherson
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