Removing Lens From Adapter: The Fotodiox Pro Lens Mount Adapter – Pentax 6×7 Lens to to Pentax 645 Body Will not release the lens.
If the release knob does not work and you can not get your lens off you will have to take the adapter apart. Three Screws need to be removed you should use a 000 Philips screwdriver or a jewelers Philips screwdriver. Make sure not to strip the screws