Originally posted by derekkite I'm not at all an optics specialist, but wouldn't a short flange difference on an MF system require quite specialized lenses to cover the sensor area? The image circle has to widen after the last element, and the longer the distance the more dramatic the angles would need to be.
Does this show up at all on native A7 lenses from Sony?
If that is the limiting factor then the lens designers can add a 'hollow tube' to the end of the lenses in order to maintain focal length. Long focal length lenses are already designed this way.
A short registration distance allows easier design of wide angle lenses.
In the extreme case the image circle doesn't widen after the last element - this is the definition of telecentricity. In theory this is required by the M4/3rds standard (which requires telecentric lenses).