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Bolex Bayonet Mount


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#1 Zach Whittaker

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Posted 16 October 2016 - 09:18 AM

Is there an adapter that will take a Bolex Bayonet mount lens and convert it to mount a C-mount camera? I've seen a lot of adapters that go the other direction.


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#2 Nicholas Kovats

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Posted 16 October 2016 - 07:45 PM

I have been obseesed with this for some time but have yet to find a third party adapter. I suspect a custom machining job is required as the FFD offset is minimal at approximately 5mm. Good luck.
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#3 Dom Jaeger

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Posted 16 October 2016 - 08:54 PM

I think there are a number of issues, which might explain why no-one has made such an adapter.

 

Firstly, as Nicholas mentioned, the difference from bayonet flange to C-mount flange is only about 5.5mm, which doesn't leave too much room for the material thickness of the bayonet flange and the lock ring threads.

 

Secondly, the large diameter of a Bolex bayonet mount sitting almost flush will hit protruding parts of a C-mount Bolex turret - the centre screw, turret lever, edge lock, and any mount caps for the other 2 mounts, including the bottom locking one which is pretty important to stabilise the turret. You'd probably find a number of other C-mount cameras that have some sort of protrusions within a 40mm radius of the mount.

 

Thirdly, the reason Bolex went to a bayonet mount for the heavy zooms of the SBM, EBM and EL era was because the weight could flex a turret and alter the crucial flange depth. So even if you custom machined an adapter and removed any protruding obstacles in order to mount a bayonet zoom, it might not be worth it for the possibly soft images or potentially damaged camera mount. Even a non-turret C-mount camera could have the front plate distorted by the weight of a heavy zoom.

 

But in theory, it's possible, and a lens support could protect the mount. 


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#4 Nicholas Kovats

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Posted 16 October 2016 - 11:10 PM

Well, Zack, you lucked out with Dom's excellent overview. He is a seperlative camera engineer and technician. I will now officially put my dream to rest.
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#5 Simon Wyss

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Posted 17 October 2016 - 03:09 AM

Good, I’d have explained the same way but Dom beat me. The Paillard-Bolex H camera was designed in 1930-31, its front and turret plates got redesigned in 1953-54 and again in 1955-56. Heavy lenses are not meant to be used with this “professional amateur” camera as it went in the publicity from 1937 on. The zoom lens challenges the older concept.

 

A choice of lens ports on a turret has a number of advantages one must learn to appreciate. I do appreciate the following ones:

  • Compact and lightweight primes
  • C mount allows the use of shim rings (with older lenses that have long mounting threads)
  • Use of the rackover system which is more easily controllable by a technician than a reflex system
  • “Vertical” shifting of a lens to some extent
  • Use of auxiliary equipment attached to the turret via one or two lens ports, for example a bellows holder

The coolest of all turrets was known with the Askania shoulder camera of 1935, it has a spring that can be wound up and then made to revolve step by step, even while the film is running. Clack, clack, clack, clack, two revolutions.


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#6 Jean-Louis Seguin

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Posted 17 October 2016 - 12:11 PM

If you happen to be talking about the later version Vario-Switar 16-100mm, Parts are available from Bolex to convert the bayonet mount to a C-mount.


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