They were the regular type thickness, not slim, B+W UVIR filters. I don't have it on me at the moment, but I think theyr were the F-Pro. What perplexed me and eventually most others was that every single other 58mm filter by anyone including all other 58mm B+W filters worked perfectly with 50mm f1.1 hood. Conversely, the B+W 58mm UVIR filter allowed every sungle 58mm screw hood and 58mm filter by anyone to screw into it. It was for whatever reason, the specific (and I mean specific) combination of the 50mm f1.1 hood screwed into a B+W 58mm UVIr, that didn't work. The hood would screw and reach the end of travle but then would never tighten up and screw round and round.
Beleive it or not, inside the 50mm f1.1 hood are threads (to allow the lens cap to catch onto....these threads actually accept a filter, although The instruction book for the lens says not to screw a filter into these threads. One work around is to screw the B+W 58mm UVIR into these threads but that leaves a big distances between the front element of the lens and the filter...as one can imagine. The other work around is to purchase the optional vented hood...which is great. Of course the 3rd work around is to use a different brand of UVIR filter. Leica does not make a 58mm one.
I believe some of those that say their 58mm B+W UVIR works with their 50mm f1.1...actually screwed their filter into the threads inside the lens hood, rather than the lens. I've seen two cases of this already. A bit strange indeed.
Dave (D&A)
