I just happened on a new-in-the-box Hoya HMC filter in a color I wanted at a good price, so I deviated from my normal B+W snobbery and bought it. On the front of the box it says "Do not use any chemical cleanser for cleaning only a soft cotton cloth allowed". Really??? I can't use Panchro like I do on everything else, or a microfiber cloth, or Rosco tissue? Yes, it was relatively cheap, but I don't want to try my normal procedures if they're going to wreck it. Has anyone violated these rules and lived to tell the tale?