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#1 andrew parrish

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Posted 03 July 2010 - 05:28 PM

Hi All

I have been given a nice set of Hexanon Prims (Konica AR). They are clean and clear, and have a very good reputation. I was looking online for C mount adapters for them, but could not find any. Has any one seen an adapter like this? The closest I found was Konica Ar to Micro 4/3.

The Hexanons have a flange of about 40.4, which, If I'm not mistaken, would make and adapter to C-mount possible, as its flange is less, at around 17.5.

If an adapter does not exist, I have access to a machinist, and could have one fabbed up. If I am not too worried about doing any focus pulling, and just want it to focus to infinity, how accurate must the adapter be? If it was less than the approximately 22mm flange difference, would it work?

Thanks
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#2 Janek Kowalski

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Posted 04 July 2010 - 04:22 AM

Hi,

I have never heard of a K/AR to C-mount adapter. But it should not be to difficult to make if you have access to a machine shop. The K/AR film to flange distance is 40.5 mm. That should give you about 23mm to play with. The adapter needs to be pretty precise. First of all there is the infinity focus issue. If your adapter is too thick you won't be able to focus at infinity. If it's too thin the lens will focus past infinity. That's not a major problem for many people - after all you focus by looking through the viewfinder. There is also the question of correct axis. If there is a fraction of a mm difference between the thickness of one side of the adapter and the other you will get sharp focus on one side of the frame and blurry contours on the other. To get an idea of how precise this is, take a look at the thickness of distance shims used by camera makers to properly sit the camera mount. These shims are calibrated in thous. of an inch.

If you decide to make your own adapter, consider using an old K/AR 2x teleconverter. Not the 7 element Hexanon converter, which is too thick, but the simpler ones available from Vivitar, Soligor, Beroflex, etc. They are a dime a dozen. Once you take the relatively small optical elements and the aperture linkages out of it, this will give you a tube of approximately the right thickness with one mount already in place. You wll then need to install the C-mount mounting plate at the other end. Sounds like a nice project. Good luck.

jk
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#3 andrew parrish

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Posted 04 July 2010 - 06:29 PM

Hi Janek

Thanks for the quick and very helpful reply. As part of the kit of lens, there was a vivitar teleconverter. I dismantled this morning, and started to mess around. It looks like it is going to work fine.

The plan is to machine a "R&D" C-mount plate that is a little on the thin side for testing purposes. Then with the optics in place, and focus set to infinity, I'll start shimming the lens until perfect focus is achieved. At this point we will use a feeler gauge to measure the distance, and then machine the final plate. Sound good?

Cheers,

Andrew

Edited by andrew parrish, 04 July 2010 - 06:33 PM.

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#4 Janek Kowalski

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Posted 05 July 2010 - 04:40 AM

Hi Amdrew,

Sounds pretty good to me. If I understand correctly, you need to ADD material between the teleconverter and your C-mount plate? Depending on how much material you're missing, you may wish to consider one of those flat spacer rings that some fellow on the web is selling as a means to mount Hexanons on Four-Thirds (not micro 4/3) camera bodies.

Look here: http://www.bophoto.c...ica/konica.html
and here: http://www.flickr.co...57612931663381/

Don't forget to mention me in the credits when your blockbuster flick comes out. :)

Cheers,

j
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#5 andrew parrish

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Posted 27 August 2010 - 09:34 PM

First prototype failed do to a machining error. number 2 comming up
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