Originally Posted by mabelsound
My S/N is 482xxx, by the way.
Mine is 480xxx, so should be the same mechanics.
I just tried Canon 34mm UV and Hoya 34mm yellow filters on the Summar, and they screw all the way in (and the Canon's glass is mounted right at the edge of the screw threads). Lining the three filters up next to each other, it's apparent that the B+W's screw thread is about 1mm deeper than the other two.
So I guess there's nothing to worry about. I'll just screw in the filter as far as it goes without forcing it, and I'm good to go. :-)
Thanks all for the info, and thanks to John for the nice UV/IR filter!