Read the specification. It's available on Boz's K mount page, (http://www.bdimitrov.de/kmp/). The only cameras that use the F ring use it's mechanical properties, but it reports the set f-stop electronically to the camera body for display purposes. Try an F/FA lens off the A position on say a MZ/ZX-5n then try an A lens the same way. The do a thought experiment after reading the K mount evolution page on Boz's site, ask yourself how the camera knows to display the aperture for the F/FA in the viewfinder.
Adam Maas wrote: >No, the aperture ring on F and FA lenses is mechanical, not electronic >as on the PanaLeica 4/3rds lens(es). > >-Adam > > >P. J. Alling wrote: > > >>The F and Fa lenses already report that set aperture to the camera body, >>if it wishes to read it. They could be used entirely electronically as >>is the new Panasonic/Leica 4/3 duo. No real complication at all, the >>extra control costs pennies to implement, and Pentax keeps is promise >>about keeping aperture rings on DFA lenses while still screwing film >>body users. Everybody wins! >> >>John Francis wrote: >> >> >> >> >>>On Sat, Sep 02, 2006 at 10:19:57AM -0400, K.Takeshita wrote: >>> >>> >>> >>> >>> >>>>Adam Maas mykroft at mykroft.com Sat Sep 2 08:49:28 EST 2006 >>>> >>>> >>>> >>>> >>>> >>>> >>>>>>400/4 with SSM would be neat. Can't see any good reason to make it >>>>>>DFA, though. DA will make it smaller, cheaper and just as good. >>>>>> >>>>>> >>>>>>Jostein >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>Actually, the size constraints on a 400 are all in the glass diameter >>>>>(for a given aperture), format is essentially irrelevant to this, at >>>>>least until you start talking LF, so there's zero reason to make it a DA >>>>>lens since it will be the same size anyways. >>>>> >>>>> >>>>> >>>>> >>>>Exactly. After certain size (say 200mm or so), there is no reason to make >>>>it a DA. >>>>Still some hope for FF wishers :-). >>>> >>>> >>>> >>>> >>>I thought a significant difference between DA and DFA was the presence >>>of an aperture ring. Sure, longer focal lengths are going to have an >>>image circle larger than an APS-sized sensor. But that in itself isn't >>>enough to make it a DFA lens. >>> >>>If, as we expect, these new lenses incorporate a new auto-focus mechanism >>>then they are designed for use mainly on new cameras. As such, I doubt >>>that Pentax would bother with the extra complication of an aperture ring. >>> >>> >>> >>> >>> >>> >> >> >> > > > > -- Things should be made as simple as possible -- but no simpler. --Albert Einstein -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net