Godfrey DiGiorgi mused: > > --- Jim Hemenway <[EMAIL PROTECTED]> wrote: > > So "K" was yet another lens type between the screwmount and > > the "M"? > > > > Was the "K" a bayonet mount? > > > > I missed everything between SM and F/FA. > > The website I mentioned, http://www.bdimitrov.de/kmp/, will give > you the details on the evolution of the Pentax K-bayonet mount. > I wasn't working with Pentax equipment then, but I recall the M > series K-bayonet lenses coming out coincident with models like > the MX, ME, ME-Super etc. > > I seem to recall some differences in the operation of the > auto-diaphragm actuation mechanism between K and M, but Dimitrov > probably has that covered. :-)
Yep - that's on the K-mount pages. In brief: with the "A" and later mounts, the response of the lens aperture to the angular displacement of the aperture operating link was explicitly defined (and differed from the previous mechanism(s), with the aim of getting more accurate control at small apertures). That's why you can't just fake an "A" pin on an earlier lens, and get Tv or P operation; even if the lens operation conforms to the most common response of those earlier lenses, intermediate aperture values would still be off (by perhaps as much as 1.5 stops, if I remember details correctly from the time this was first discussed).
