Perfect filter for CV 15mm V1
Bought a 39mm UV/IR filter off eBay from a Chinese seller and just received it today. I was ready to use the blu-tac trick to get 39mm filters to stay but it seems that this 39mm filter has a slightly wider shell than the B+W ones. Not sure if it's a coincidence but it's just the right radius to squeeze into the 15mm's built in "petals" and holds quite firmly!
For those interested, you can get them from "rocolax_profilter". Not affiliated with him/her at all and thought it'd be useful information for those of you using the 15mm on an M8. BTW, the filters go for just $22 and from my initial tests, seem to work the same as my B+W filters. Seller also claims they're made from Schott glass.
Tags for future googlers:
Voigtlander 15mm filter screw mount