RB lens shade quandry.

[largely]

This is making me crazy.
I wrote in another thread that I had purchased an RB compendium shade and it didn't fit. Several members advised that it was missing the adapter ring. They were correct. So even though I already had two of these rings I thought they must be the wrong ones and I purchased another ring (for the G2 shade) from KEH.
It's exactly the same as the ones I have so I sent it back.
The problem is that the diameter of ring which is supposed to mount the shade is just under 3 in. (2.975 to be exact) and the bore in the back of the shade is 3.265 in. a difference of over 1/4 in.
The shade is marked Mamiya Japan but bears no part number.
I called Mamiya and talked to their tech guy. He said there are only two shades, the G2 and G3. I know the one I have isn't a G3. The visual differences are obvious and he says the G3 ring is over 3 3/4 in. in diameter. He thought that maybe I have a 645 shade (which has a much smaller threaded end ) but he wasn't sure and he didn't seem interested in finding out.
If anyone has a 645 compendium I'd appreciate it if you'ld measure the diameter of the counterbore in the back of the shade and let me know if it's just over 3 1/4 in. I don't have a lot more hair to pull out.
thanks,

Larry

 

[keithwms]

I use the screw-on shades with my rb and rz, they are fine. They get the job done at low cost.

 

[iamjanco]

Larry,

I have the G3. If you need measurements, let me know.

Jan

 

[largely]

Hi Jan,
I'd appreciate it if you could measure the counterbore in the back of the shade (where the ring fits) and tell me the diameter of same.
thanks a lot,

Larry

 

[iamjanco]

Hi Larry,

Sorry it took so long to get back to you. I just measured the counterbore on the G3 and confirmed it's 3 3/4 inches, as the tech guy at Mamiya told you. Hope that helps.

Jan

 

[largely]

Hi Jan,
That's what I thought .
I guess the one that I have will remain a mystery since the Mamiya' guy doesn't recognize it (though it has the Mamiya logo on it). I'll just machine a ring to reduce the size of the bore and bond it in.
Thanks for taking the time to help,

Larry