Originally posted by cooltouch: Sorry, but can I ask a question here about the inner and outer bay tubes? I'm not at all clear on how they would be used. What are the advantages and disadvantages of each type?
It's not a matter of advantages but of compatibility. The Pentax 6x7 bodies and successors have 2 lens mounts: An inner bayonet mount for most of the lenses, and an outer breach-lock mount for the 400mm, 600mm, and 800mm lenses. If you have any of those longer breach-lock lenses and want the close focusing capability provided by extension tubes, then you need the "outer" tubes. If you have only the shorter (300mm and less), bayonet mount lenses, then the more readily available "inner" auto extension tubes are sufficient.
There were 3 different sizes of extension tubes in the "inner" bayonet mount, and 2 different extension tubes in the "outer" breach-lock mount.
Interestingly, the P67 bellows uses the outer breach-lock mount on the camera side, but the bayonet mount for the lens side.
One of the things I love about the P67 engineering is that it comes with two mount systems right out of the box. And for some reason when they built the 500mm lens they used the bayonet rather than the breach-lock. This camera body is way over-engineered when it comes to the lens flanges. If only the shutter and wind mechanisms were as failsafe.
