Lucas Rijnders wrote: > On Wed, 27 Sep 2006 17:48:34 +0200, Adam Maas <[EMAIL PROTECTED]> wrote: > > >>Lucas Rijnders wrote: >> >>>Op Wed, 27 Sep 2006 16:07:19 +0200 schreef Adam Maas >>><[EMAIL PROTECTED]>: >>> >>> >>>>Lucas Rijnders wrote: >>> >>>>>Anything on backward/forward compatibility of the USM and the old AF >>>>>system? Did your rep explain the AF/MF switch on the lenses? >>> >>>>The AF/MF switch on the lens will work just like it does on Canon USM >>>>or >>>>Nikon AF-S lenses. It's not exactly unique. Does exactly what it looks >>>>like it will do (Allows you to turn off AF on the lens). >>> >>>I am not familiar with Canon or Nikon lenses. Could you explain what the >>>point is, given that you can turn off AF in the body, and that USM (at >>>least the Canon variant) allows manual focus in AF mode? >>> >>>Genuinly interested, >> >>Note that not all USM lenses allow full-time manual focusing. >>Micro-motor USM lenses (all low-end Canon USM lenses as well as the >>Nikkor 18-55 and 55-200) do not allow it, except for the 50 f1.4 USM >>which is clutched like a DA lens (the 50 is only micro-motor USM for >>size reasons, ring-type would make it notably bigger). > > > I would not expect this solution with Pentax: they have good old in body > AF for budget lenses...
So does Nikon, and Canon has non-USM drives as well. Cheap USM is quiet and at least as fast as screwdriver AF. > > >>The switch on the lens disengages AF in the lens directly, and tells the >>body that it's been done (ensuring nothing bad happens to the motor). >>It's also much more conveniently located than the on-body switch > > > Depends on what You're used to, I think. On the one EF lens I used (a > consumer 28-80, and I used it very briefly) I did not find the location > that handy... > The cheapo lenses have cheapo switches. The good USM lenses have nice big switches that are sometimes (as Cotty notes) too easy to switch. > >>typically. Note that while USM allows MF override, in AF-S mode it works >>just like the clutched DA/D-FA lenses, you need to let it lock first >>then override. > > > That's a point. We'll see how it is implemented: two AF/MF switches can > potentially be great fun for the helpdesk (will it be an AND or an OR > situation?) > > Thanks for the explanation. -Adam -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
