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2.215mm C-mount Spacer


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#1 Glenn Brady

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Posted 16 March 2009 - 12:06 PM

Can anyone recommend a source for an off-the-shelf 2.215mm C-mount spacer that will make it possible to accurately scale focus 75mm, 100mm, and 150mm H16 RX lenses on an H8 RX camera?
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#2 kevin jackman

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Posted 02 April 2009 - 10:59 AM

Can anyone recommend a source for an off-the-shelf 2.215mm C-mount spacer that will make it possible to accurately scale focus 75mm, 100mm, and 150mm H16 RX lenses on an H8 RX camera?


well you could mabye machine down the smallest extension tube. i thought about that. jk optical will also do some machining. one problem that apparently exists is the prism isnt the same as the 16 models so it may affect image quality. bolex told me this sort of conversion doesnt work well. my plan was to swap prisms. i dont need to use the original primes. they wont cover ultra8 anyway. i was also planning on finding a non reflex h8 if they are around so i can install a pellicle viewing system so non bolex lenses can be used.
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#3 Jean-Louis Seguin

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Posted 02 April 2009 - 12:15 PM

With a spacer that thick between the lens and the turret, your lenses will by hanging on by almost no thread.
This is recipe for disaster.

A better solution is to have one of your turret openings modified so that it will have a mount which is the proper distance for accurate focusing and has sufficient thread for a solid mounting. JK used to do this modification.

Another thing: I wonder how you arrive at the distance of 2.215mm? Did you figure this it out experimentally?

Cheers,
Jean-Louis

Edited by Jean-Louis Seguin, 02 April 2009 - 12:16 PM.

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#4 Ian Cooper

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Posted 02 April 2009 - 12:22 PM

The amount of thread on the lens (at least on my C-Mount lenses) seems to protrude about 4mm. This means with a 2.215mm spacer there would only be 1.785mm of thread protruding out of the spacer to actually engage with the threads on the camera. The C-Mount itself is 1" diameter by 32tpi, so 1.785mm would equate to just 2.25 threads worth of engagement (against about 5 normally). Certainly for larger lenses that might put a bit of strain on the threads - especially if the first thread on the lens/camera is already a bit worn.

If the distance was greater than 4mm you'd be able to make an adapter which screwed onto camera, then the lens screwed into the adapter.

Whilst I don't know for sure, I very much doubt you'll find what you're looking for 'off the shelf'.


Edit: Lol Jean-Louis - clearly we are thinking along much the same lines and posting at the same time as well!

Edited by Ian Cooper, 02 April 2009 - 12:25 PM.

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#5 Jean-Louis Seguin

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Posted 02 April 2009 - 01:18 PM

Edit: Lol Jean-Louis - clearly we are thinking along much the same lines and posting at the same time as well!




Yeah, just 7 minutes apart. Great minds think alike!

Jean-Louis
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#6 Glenn Brady

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Posted 04 April 2009 - 07:21 AM

I wonder how you arrive at the distance of 2.215mm? Did you figure this it out experimentally?
Cheers,
Jean-Louis


I assumed the spacer thickness would be the difference in the flange focus distance of the H8 RX and H16 RX.

When I spoke with Jaakko Kurhi late last year, he told me that he'd retired. That raises another question. Is anyone doing DS8 conversions of Bolex H8 RX cameras anymore? Maybe Ruedi Muster?
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#7 Jean-Louis Seguin

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Posted 04 April 2009 - 08:12 AM

I assumed the spacer thickness would be the difference in the flange focus distance of the H8 RX and H16 RX.

When I spoke with Jaakko Kurhi late last year, he told me that he'd retired. That raises another question. Is anyone doing DS8 conversions of Bolex H8 RX cameras anymore? Maybe Ruedi Muster?




Hi Glenn,

If you just want your turret modified, that is something I can do. Could cost around $200 for the work.

Jaakko's modification involves the manufacturing of a new gate, new sprockets and new claws. I am assuming he has run out of those parts a long time ago. Also, demand for conversions must be infrequent as there are already a lot of those cameras in the marketplace and it should not be too difficult to purchase an already converted camera. They pop up on eBay from time to time.

I am unfamiliar with Herr Muster's conversion and whether it is still possible to have it done.

Historical note: Many, many years ago, Swiss Professional Camera Corp. in NYC, who were the Bolex service representatives for North America then, also offered their own conversion. I don't know what happened to this company and why they disappeared from the landscape.

Cheers,
Jean-Louis
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#8 Glenn Brady

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Posted 04 April 2009 - 08:39 AM

Hi, Jean-Louis

Thanks for this information. It's good to know that you can perform this modification. Reviewing comments in this thread, I now realize a spacer wouldn't be practical.

Regards,
Glenn
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#9 Bernd Steinert

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Posted 30 April 2009 - 04:17 PM

I assumed the spacer thickness would be the difference in the flange focus distance of the H8 RX and H16 RX.

When I spoke with Jaakko Kurhi late last year, he told me that he'd retired. That raises another question. Is anyone doing DS8 conversions of Bolex H8 RX cameras anymore? Maybe Ruedi Muster?


Hi Glenn,

Ruedi Muster is still doing Bolex H8 DS8 conversions. He charges around 2800 Swiss Francs for this service. You have to mail him your own camera but you can also buy a Regular 8 Bolex camera from him to be converted. His quality is excellent.

Bernd
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#10 Glenn Brady

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Posted 01 May 2009 - 10:23 AM

Hi Glenn,

Ruedi Muster is still doing Bolex H8 DS8 conversions. He charges around 2800 Swiss Francs for this service. You have to mail him your own camera but you can also buy a Regular 8 Bolex camera from him to be converted. His quality is excellent.

Bernd


Hi, Bernd

That's about four times what Jaakko Kurhi was charging for a DS8 conversion, but I guess the devaluation of the Dollar may explain some of it. It's good to know somebody is still doing this work.

Glenn
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