Originally posted by atlnq9 Or rip apart a Pentax 645 LS lens. The pins are probably sending some kind of signal to the camera that it is LS. Could see if Hartblei could use this 645 mount with the pins and electronic chip (or whatever is in there) when they assemble the adapter. Would make cost go up a lot I bet. But would allow the RB lenses to function exactly like Pentax 75mm leaf shutter lens...
There is no "signal", Pentax LS lenses are completely mechanical. The shutter actuation is tied into the aperture stop-down lever. When the camera stops down, the leaf shutter blades close, the main shutter opens, after a fixed delay the leaf shutter reopens for its exposure, the leaf shutter closes, and the main shutter closes after its exposure time has been complete. Depending on the precise model the leaf shutter may or may not reopen until you cock it again (the 6x7 90 LS reopens, the 6x7 165 LS supposedly doesn't).
The camera knows nothing about when the leaf shutter opens and closes and in fact doesn't even know there's a second shutter in the lens. You must set the FP shutter to open for longer than the leaf shutter (at least 1/8th second) or else you will cut the exposure short, and the metering is based on the camera setting, not the lens setting.
It might be possible to create an adapter that would simply hold a Mamiya 7 lens open, assuming you had adequate register distance and all that other jazz. Essentially what you are suggesting is a permanent bulb exposure, you might be able to attach the contacts to a logic analyzer, trigger a bulb exposure, and then build an adapter that just sends that signal without closing it. It would probably require power continuously to hold the aperture open.