Minolta F.ROKKOR-QF 1:5.6 f=200mm

[radeks]

Hi all,

Since it was hard to find information on Minolta F.ROKKOR-QF 1:5.6 f=200mm lens and it's applicability to 8x10, I thought I'd post here my result. The lens, which is a "fax" process lens, is possible to fit into Shanel - 5B shutter, I did it with 3D printed adapter rings. The cells are 0.7mm farther apart than in original barrel but it doesn't seem to impact image quality. Center of image is sharp fully open (1:5.6) with blur around edges, I'd say pleasing effect. When stopped down to 1:11, it's sharp across the film. The lens can cover 8x10 with small movements. Considering it can be found on auction places quite cheap and the Shanel - 5B shutter cost is also reasonable, I use it as an affordable wide angle on my Intrepid 8x10.
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I'd be happy to answer any questions,
cheers,
Radek.

[xkaes]

I've often wondered how these FAX lenses would perform on LF cameras. Seems like a good inexpensive option for some -- if a spare shutter is available.

How did you manage to adapter it to the 5B?

[Mark Sampson]

Nice work. As you know, wide-angle lenses for 8x10 are rare, often very large, and usually expensive- looks like you've solved that problem!

[xkaes]

Makes me wonder how many completely-usable FAX lenses end up in the dump every day.

[Dan Fromm]

Interesting. I'd thought that those Minolta lenses' elements weren't mounted in cells that could be unscrewed.

[xkaes]

Exactly why I asked "How did you manage to adapter it to the 5B?"

[radeks]

It was possible to unscrew the cells, my tool was "strap wrench" for sink. Image is worth thousand words ;-).
BTW, it's still a heavy lens in shutter, 1000g!
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cheers,
Radek.

[Dan Fromm]

Ah! Thanks for the reply.

[David Lindquist]

So did the cells then screw directly in to the Shanel shutter with the correct spacing, seems unlikely. Or how was this done?

David

[radeks]

No, I had to create adapter rings, 3D printed, one for rear cell and one for front cell with internal thread fitting the cell and external thread fitting the shutter. The cell spacing is 0.7mm longer because bottom cell was hitting shutter aperture if I was trying to get closer. The 0.7 mm longer spacing doesn't seem to have any noticeable effect on image quality.

Radek.

[David Lindquist]

Thank you. 3D printed, nicely done!

As far as the spacing, one hears that this must be "exact", but of course nothing is exact, everything of this sort has a tolerance. What the tolerances are in lens spacing though, well I've never really seen any figures. I think some lens designs are more finicky about this than others.

David

[Dan Fromm]

Thank you. 3D printed, nicely done!

As far as the spacing, one hears that this must be "exact", but of course nothing is exact, everything of this sort has a tolerance. What the tolerances are in lens spacing though, well I've never really seen any figures. I think some lens designs are more finicky about this than others.

David

David, my friend and coauthor Eric Beltrando once told me that plasmat types were not particularly sensitive to cell spacing errors.

OP, the late Steve Grimes once remounted a 65/8 Ilex lens for me. It had been in an Ilex electronic #00 for which I didn't and don't have the control unit and I wanted it in a Compur #00. The two shutters have the same threading but the Compur's tube length is greater. Steve machined the Compur's front tube; he didn't shorten it, he opened it up to make room for the front cell's "shouldner."

[StrangleMeRandy]

I'd just like to see pics taken with the lens :~) I'd very much like some Rokkor glass for my 5x7, my lensboard isn't big enough for a massive Shanel or Ilex shutter, though.

[Curty]

Hi all,

Since it was hard to find information on Minolta F.ROKKOR-QF 1:5.6 f=200mm lens and it's applicability to 8x10, I thought I'd post here my result. The lens, which is a "fax" process lens, is possible to fit into Shanel - 5B shutter, I did it with 3D printed adapter rings. The cells are 0.7mm farther apart than in original barrel but it doesn't seem to impact image quality. Center of image is sharp fully open (1:5.6) with blur around edges, I'd say pleasing effect. When stopped down to 1:11, it's sharp across the film. The lens can cover 8x10 with small movements. Considering it can be found on auction places quite cheap and the Shanel - 5B shutter cost is also reasonable, I use it as an affordable wide angle on my Intrepid 8x10.
235248
235245
235246
235247

I'd be happy to answer any questions,
cheers,
Radek.


Hi Radek,
I've got 2 of those (195mm with 6.5 aperture and one exactly like yours 200mm and 5.6). I am planning to do a mechanical iris and mount that on it. I don't have the need for fast shutter speeds as I usually do my shoots directly on paper.
Mine seems to be in a different kind of mount than the picture you posted though, and the mount has holes for screws. So not sure if it's exactly same as yours.

Kind Regards

Questions,
Did you only needed 1 strap wrench tool? I have never seen one of those here where I live.
Also, would you be so kind to share your .stl or cad models for the rings?
Kind Regards

[xkaes]

Questions,
Did you only needed 1 strap wrench tool? I have never seen one of those here where I live.

Kind Regards

Those strap wrenches are easy to get at any hardware store. They come in various sizes -- like regular pipe/monkey wrenches. And as with normal wrenches, if you are lucky, you only need one. The head is a rubber strap which is much better than a metal head to avoid scratches.

[radeks]

Hi Curty,

the adapter rings were designed in FreeCAD, design files are about 5MB for each ring. When exported as stl, top ring is 13MB, bottom ring 17MB. I think it's too large for publishing on the forum, let me know how should I share it.
BTW, here are my measurements of F-Rokkor-QF 200mm, measured with calipers so take it with pinch of salt but design based on these measurements worked.

Top Cell: thread 58mm x 0.5mm
Top Distance to aperture: 20mm
Bottom Cell: thread 58mm x 0.5
Bottom distance to aperture: 20 mm

Top to bottom stop distance: 41.25 mm
Top to bottom cell external distance: 66.10 mm

cheers,
Radek.
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