Yet another post that misses the most important point.
Those two additional contacts are *power* contacts. That's all. There's no signalling going on over those contacts, so there's no need to play games with polarities, pulse modulation, or the like. They are there solely to provide power to electric motors; more power than is needed for the CPU and other circuitry in the lens. It's just like that power supply box in your PC. You can use it to power a hard drive, a CD drive, or any other peripheral you like. All the control signals go over a completely different path. In the case of a Pentax camera and lens (KAF or later, naturally) that's the digital signal pin (the one that isn't there on a KA mount). You don't need any new pins - a digital messaging protocol can be extended to new message types very simply. If a lens gets a message it doesn't recognize, I would expect that it just ignores it. On Thu, Aug 31, 2006 at 02:13:43PM -0500, Gonz wrote: > I would imagine they would do something that would prevent that. I.e, > I've seen similar situations where they do something simple like switch > the signal polarities or provide some type of pulse modulation or high > frequency signal. > > [EMAIL PROTECTED] wrote: > > I would hope they would work as manual focus lenses. It that's true, > > they should work on old bodies. Given the proclivities of people to thy > > things that physically work, I hope you can't damage a USM lens or PZ > > body if they are mated with each other... > > > > Kostas Kavoussanakis wrote: > > > > > >>On Thu, 31 Aug 2006, Sylwester Pietrzyk wrote: > >> > >> > >> > >> > >>>Exactly. One must have lenses with built-in USM motor for USM to > >>>work :-) But I guess new mount would be back compatible, so older > >>>lenses would work the way they usually did ;-) > >>> > >>> > >> > >>Would the opposite also be correct? Would USM lenses work as AF lenses > >>on screw-driver bodies? Would they even work as MF lenses? > >> > >>Kostas > >> > >> > >> > > > > > > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
