This is my first post to this august group. I have been looking into this adapter for use on my OM gear, Canon 5D and possibly other mounts as well. I was going to get the 645 front end and possible the M42 camera end and then get a custom adapter to OM
and the a commercial M42-Eos. Mirex thought that maybe it wasn't such a hot idea.
I wanted to save a few mm of extension. This would would used for macro so infinity focus is not a big deal. This is what Mirex emailed back:

"Dear Mr Mike,

this would be a solution.
We, however, do not find this solution optimal since you do not achieve with your camera infinitely any more.
As well is it comes to easy deviations of the horizontal and vertical orientation of the TS-Adapter due to tolerances of the M42 threads at your camera.
These deviations are not available at a bayonet connection.

Best Regards,"

I am not sure there would be much play in the M42 mount, but perhaps I am wrong.
Thought I should check here. Thanks for any comments.

Mike

Welcome to the Alternatives forum. Right now, we're more of a November group.

I have both a Mirex M645 to EOS adapter and a Mamiya M645 T-S Auto-Bellows system, but that's because I have a bunch of M645 lenses to use on them. In my experience, the folks at Mirex know what they're talking about. OTOH, if you know what you want, then order it.

Can you describe exactly why you want the Mirex adapter ? If you want to use OM lenses on your 5D for macro, then maybe you should look for an OM bellows system. If you want to use Mamiya M645 lenses on OM cameras, then you're in an alternate alternative situation.

Thanks for your comments. I am planning to use a M 120 macro and OM bellows lenses
with the Mirex adapter for both the OM body and Canon 5D. The image circle of the OM
135 f4, 80 f4 and 38mm will support this. A custom adapter will be required to adapter the OM autotube to the Mirex (lens end) which can be constructed. The T-S bellows for OM was never brought to market but the lenses were constructed to support it. Novoflex has one that can work but is not very portable. I thought the Mirex was just the ticket but am worried about the M42 comments from Mirex. I could go completely bayonet mount and sacrifice a few more mm of extra extension. I don't have much (read any) experience with M42.

Mike

M42 is a fine mounting system. In fact, I think most of my M42 adapters provide a more secure mount than many bayonet adapters, as the M42 just screws in until its tight, while the bayonets need proper fit and function for both the jamming/camming action and the stop-pin or stop-lever to be secure. OTOH, I agree in general with the comments from Mirex, as you always get a bit more movement when you add more attachment devices.

Thanks for your observations. Only way to avoid an extra adapter is to go with the
Hasselblad Mirex that has a T-mount. I get an extra several mm of extension when using the Zuikos and can't use a Mamiya 120. The hassy 120 is more expensive and perhaps not really much better.

http://www.luminous-landscape.com/essays/back-testing.shtml

Another option is to go with the Mamiya and Canon and then Canon to OM---again 2mm more extension but at least no other adapters at least on 5D. As it is unlikely anyone would have 1st hand experience, will likely have to make my best guestimation of the optimal arrangement. I'll certainly listen to any biases as this is the best place.
I hope I am fretting about nothing, but it could be an expensive mistake.
Thanks again for commenting.
Mike