When the Pentax 67 200mm f/4 is mounted on the Canon R8 using a standard Pentax-67-to-RF adapter, the lens behaves exactly as it was designed: a true 200mm f/4 telephoto. The adapter does not change the focal length or the aperture. It simply positions the lens at the correct distance from the sensor so the optics can focus properly, including infinity. Because the Canon R8 uses a full-frame sensor, the entire photographic experience with this lens becomes very natural.

The Pentax 67 mount is technically obsolete, but calling it irrelevant would be a mistake. The system was created in 1969 for the large Pentax 6×7 film camera, later renamed Pentax 67, and it remained in production until the early 2000s. Pentax eventually ended development when digital photography overtook medium-format film systems, and no modern digital camera bodies use the Pentax 67 mount natively. In that strict sense the mount belongs to a discontinued ecosystem.