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12-11-2010, 10:47 PM   #1
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I'd like to adapt a Nikon lens TO the Pentax 6x7...possible??

Yes I know that sounds dumb, smaller image circle, etc.

However, I checked and my Nikon 200mm Micro lens at closest focusing just about covers the whole film area when I hold it up to the mount, just a little vignetting at the corners (and I hadn't even stopped down). This is the sharpest lens I've ever used so I'd just like to try it on my 6x7 for fun.

Anyway, is there anyway to do this? I know there probably isn't an off-the-shelf product. I can't fabricate it myself, I don't have the tools/time (BTW I'd be willing to pay someone to do it if they wanted).

Anyone got any ideas?

12-11-2010, 11:44 PM   #2
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Glue (epoxy, etc) a Nikon rear cap centred in a 6x7 body cap and then cut a hole through the middle? Probably good enough for a cheap prototype so that you can shoot a few rolls of film to see if the idea will work out in practice. All you should need in the way of tools is a tube of 2 part epoxy from the hardware store, some sandpaper to rough up the mating surfaces for better adhesion and a sharp hobby knife to carve out the hole. Building up epoxy around the perimeter of the lens cap will provide more surface area for bonding and should reduce the likelihood of the joint breaking apart. Depending on how strong the joint ends up being you may need to support the lens's weight separately.

For a more permanent solution I would probably look at grafting a female Nikon F mount from a cheap or damaged film body onto a 6x7 male mount from an extension tube or a badly damaged lens. For a one off project dimensioning and machining the mounts from scratch would likely be far more expensive than scavenging the parts and building an adaptor plate so they can be screwed together.
12-12-2010, 03:05 PM   #3
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Thanks for the suggestions...I had already priced an F-mount but I hadn't thought of buying a really cheap busted film camera! Good idea. The #1 extension tube for the Pentax surely can't be too expensive. I'm just not sure how'd I'd graft them together...

For the short term I do think I have an extra body cap for the 67 and maybe a rear cap I can sacrifice for my Nikon...

Thanks
12-12-2010, 08:43 PM   #4
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Depending on the dimensions a metal plate over top of the 6x7 mount or a plug inside of it will provide a surface to which a Nikon mount can be attached. The same approach is used for attaching mismatched engine and machine parts. If amount of extra extension added between the lens and the body isn't too critical it should be a fairly simple machining job.

12-13-2010, 04:01 AM   #5
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The mounting flange to register (film) distance on the Pentax 67 is 84.95mm, whilst it is 46.5mm for the F-mount. That is about a 40mm difference that you will lose in focussing range, leaving the lens to be only useful for very close-up work, which is what I presume you intend to do with it.

I'd suggest using a 67 mount taken from an inner extension tube - the mount can be removed from the rest of the tube by unscrewing three small screws and three tiny dowels. Try not to strip the dowel head with the screw driver as you will then have to drill it out in order to remove it.

Then remove the F-mount from the Nikkor. At that point, you can machine (use aluminium) a short connecting cylinder than can be attached to the Nikkor lens sans F-mount, following the bolting configuration of the F-mount and adapting the cylinder accordingly. Then drill and thread three mounting holes at 180 degrees in the outside top of the cylinder to accept the 67 mount - 2mm threading will do. Drill three corresponding 2.5mm dia holes in the face plate of the 67 mount taken from the extension ring and attach it to the cylinder - I'd use 5mm length screws with hex heads.

I would suggest finding a local machine shop to help you with the fabrication of the aluminium cylinder. If this is too difficult for you, contact me privately, as I have been adapting various lenses to the 67 using this methodology for a while now, though not any F-mounts, and my machinist has learned all the ins and outs of it.

I am a bit suprised that the area of illumination of the Nikkor is sufficient for the 67, but maybe you will be lucky. I had been told it was insufficient for several of the lenses that I adapted, but they all worked out fine.

Best, Alan
12-13-2010, 09:54 AM   #6
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Thanks for the informative reply!! I will have to look into a machine shop around here and see what I can make.
12-13-2010, 11:13 AM   #7
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On most lenses with this focal length on SLRs, the optical design is somewhat asymmetrical, meaning the focal length will be different (usually longer) when the lens is reversed. If you are considering using this lens for any infinity work, reversing it via a Pentax reverse adapter + step ring may work. You could get a rough idea if this could work by holding the reversed lens in front of your 67 body with mirror up to see if it will focus light from infinity at the shutter curtain.
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