Pentax (Minolta) lens mount to large clamp-on mount adapter?

Hello. Among my odd items is this Minolta lens to clamp-on mount.

I think it's a MN lens mount - it looks close, but not exact.

The other side of the adapter is a grooved rim, of the kind that would accept screw clamps.

Clearly I am ignorant of just about everything about this adapter.

Does anyone recognize it? Thank you/

Just so I'm not treading water in the wrong forum - can someone please verify that this is a minolta mount?

The mount itself looks Minolta, but the moving pin seems to be in a different location.

Thanks/

P.S. Is the other side a T-mount, in a different than usual diameter? Is there such a thing?

Brian, that's a Pentax K-mount, not Minolta.

I too am puzzled about T-mounts as there do seem to be different diameters. There should of course be another ring with screws which engage with the groove seen in the picture.

Thank you, John. The mating ring with clamping screws would be on the receiving optics, yes?

I think these mounts are for telescopes, large microscopes, CRT displays, lab equipment, etc., not for lenses.

But i've never seen one this size before - it appears to fit in a 54mm opening.

It might help if you included a ruler rather than a stuffed toy.

There were several interchangeable mount systems apart from T and T2. IIRC, Vivitar had a TX or T4 system. They're fairly rare, since they were quite complicated things that coupled to the aperture mechanism directly.

Also, T2 mounts all came in two parts: A socketed part that fitted to the camera, and a flange that fitted the 42mm x 0.75 lens thread. The two halves were held together by pinch-bolts (grub screws), but there was no standardised size for the flange and its corresponding socket. One maker's lens ring wouldn't necessarily fit another maker's camera socket, and even if they did, they might not give the correct register distance.

Anyhow, the thing shown looks like a camera mount, not a lens adapter. Most lenses have a male thread or bayonet, not a female socket. AFAIK, only Canon's FD mount had a female bayonet socket on the lens, and it looked nothing like that.

Tamron Adaptall mounts bayonet onto the lens, but that looks nothing like an Adaptall mount either.

Is it possible it's part of an adapter from medium-format (Pentax or Mamiya 645) to a 35mn camera?

Some clue to size really would help.

Thank you. Yes, it is the mount that would be on the camera body. That's why I hedged calling the other side a T-mount -

even though it might be missing the bolt part - because the 'socket' side was so wide.

It's a 54mm diameter rim. As the pictures show it's quite large compared to the mount.

I don't know of any T's this size. and it doesn't make sense to have mounts for lenses on both sides of an adapter.

My guess now is that it's for mounting lenses on a specialty camera, maybe one that takes lensboards?

P.S. Shouldn't I move this thread to the Pentax section?

Thanks.

I'm 90% certain that it's the lower lens mount from something similar to an Bowens Illumitran slide duplicator. The lens would bayonet in on one side and the other side would mount in an opening on the lower part of the bellows. The groove is there to allow the lens to be rotated and then held in place by a set screw so you could make sure the aperture ring was centered in the front of the unit

I'm 90% certain that it's the lower lens mount from something similar to an Bowens Illumitran slide duplicator. The lens would bayonet in on one side and the other side would mount in an opening on the lower part of the bellows. The groove is there to allow the lens to be rotated and then held in place by a set screw so you could make sure the aperture ring was centered in the front of the unit

 

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Thank you I will look into that.

I think it's a reverse adaptor K or a reverse ring light adaptor K. More explanation can be found on the Pentax K-Mount Page in the section dedicated to macro.

I searched 'Pentax K' in the macro forum, and came up with 0 results.

Could you clarify your directions, please? Thanks.