The 28-105 power zoom (the lens I mounted on my MZ-S to test) changes length by perhaps 4mm over the whole focus range. That's about 1/3 of the change in length due to the zoom.
So the MZ-S loses closer to a quarter than half the potential benefit if it were to change the focus as well as the zoom. On my other two power zoom lenses, neither focussing nor zooming affect the length of the lens in any way at all. Joe Wilensky mused: > > But are any of them power zoom lenses? I think most of the IF lenses > replaced older power zoom designs. The 100-300 power zoom doesn't > change size at all when zooming, only when focusing. Others, like the > 28-105 power zoom, can change size nearly as much from close focusing > as they can from zooming. It's just too bad half this feature is lost > on the MZ-S, but it is a minor complaint, at best. > > Joe > > > > >John Whittingham mused: > >> > >> > According to the FA manual, the power zoom lenses retract but do not > >> > focus to infinity with the MZ-S. > >> > >> Strange on such a high spec body, Pentax eh :) > > > >Not if you assume it's going to be used with IF lenses ... > > > >With most of my lenses the change of length with focus isn't > >all that great (even discounting the IF examples). But the > >change of length with zoom is much, much larger. > >
