Originally posted by Erich_H it's easy math for me!
Glad to help save you $200 USD and the pain of waiting (and waiting). I don't even have my Q yet, and I received a Canon FD - Q mount adapter already. I have an old AE-1 and some really nice, fast lenses for it, so the Q might not hit the diffraction limit with them.
Sadly, I'm almost positive I'll need to find some black velvet or matte paint to put inside the adapter (to reduce internal flare)! It may have been anodized black (or dark blue?), but it is still very shiny metal in the
cone-like descent to Q lensmount, and the image circle from an FD lens is much bigger than the opening to the sensor...
The Pentax one, as expected, was a rough, pebbled black surface inside, and with a very matte finish. No light bouncing off that!