Dave, I've got 1.25x and 1.4x magnifiers on the way. Trying to decide between a 90 summicron and a 135 elmar. The 135s I've seen on eBay come in two flavors - the one with the scalloped focusing ring and external hood, and the 'newer' E46 one with the integrated hood. The only thing that's holding me back on the 135 is the fear of focus shift / front/back focusing. I'm also hearing/reading that the two versions share the same optical design and IQ, with the only difference being body design. Is this correct?Yes, the link you provided to the 135mm f4 was the version I was refering to....but you should have no trouble finding one for much less!
The alternative, of course, is a nice 90 cron, which I personally prefer over a 75/1.8 (CV) - how hard is it to find a good copy? I'm seeing prices around USD1.6k for a fairly clean example, and frankly, I'd rather pay for a good copy than save a hundred or two and end up with something which won't focus right on the M9.
What do you think? Just go for it?