This may be off-topic, but is the "compose with the front, focus with the rear" also responsible for why it is so darn difficult to do high magnification with my Mamiya RB67?

Up to 1:2 or so things are easy enough, but beyond that (> 1:1), the physical act of moving the lens closer to the subject as the bellows is extended actually overwhelms the intention of bringing the focus point closer to the lens, so that focusing "closer" actually moves the plane of focus further away from the camera.

It would be interesting to devise a mechanism of attaching the lens to a tripod / focusing rail, thereby freely moving the camera body backwards when focusing. Hmm...

On a related note, Bosaiya, I would *love* to see some of those 20:1 mcro shots on 4x5, I have never seen examples of such extreme magnification. I can imagine you need some very strong light on the subject to focus and compose, as well as extreme bellows extension and a subject mere millimeters from the lens. This will take some doing I imagine. 2:1 on 6x7cm is tough enough already.