You're right, I had forgotten about the digital control signal pin. That would prevent any compatibility problems.
In any event, if you read my original post, I was not speculating that they would do any type of power hacking to prevent old lenses or old bodies from breaking. I was merely mentioning that I've seen a *similar* situation (power *was* the control) where they did wierd stuff like polarity or pulsing for backwards/forwards compatibility, it wasnt Pentax, it wasnt even a camera. [EMAIL PROTECTED] wrote: > Yes - they just supply power. All the time. It's not switched. > As long as the camera is turned on, there's power available. > As they don't also send the "change the focus" commands over the > digital command channel, nothing else happens. There's no risk. > > > On Thu, Aug 31, 2006 at 03:46:06PM -0500, Gonz wrote: > >>I think you missed the point actually. Yes, they are power pins, but >>the new lenses are going to share those contacts with the old power zoom >>lenses, and the new camera bodies are going to share the pins with the >>old PZ camera bodies. The new camera bodies might have to support the >>old power zoom lenses, or they might choose to ignore it. The bigger >>problem is what do the old PZ bodies do with the new USM lenses. Do >>they just supply power to them John and hope for the best? I dont think >>they will risk that scenario. >> >> >>[EMAIL PROTECTED] wrote: >> >>>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 > > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
