On Fri, Oct 13, 2006 at 08:16:05AM +0000, mike wilson wrote: > > > On 13/10/06, John Francis <[EMAIL PROTECTED]> wrote: > > > > > > My guess would be that we'll begin to see new lenses that communicate > > > far more information over the digital signal pin (such as, say, the > > > actual aperture the lens is set to; far more accurate than relying > > > on the position of a mechanical actuator). > > I don't see how that would work. The aperture mechanism is just that; a > mechanism. There has to be some coupling to the electronics to create the > digital signal. The alleged propensity for mismeasurement (all those > inaccurate 35mm bodies for all those years....) seems to be there until some > form of totally electronic aperture, er, mechanism is created.
Not really. All you need in the lens is an optical encoder coupled to one of the actual aperture blades, so you can read the position to any desired accuracy. No moving parts (other than the aperture diaphragm itself). Just adding that, rather than relying on positional accuracy of a lever, would eliminate all the inaccuracies caused by bent couplings, etc. > It seems to me, looking at opinions of lens types expressed here over the > years, that putting the mechanical link to the aperture coupler signaller in > the lens (which is what A and later lenses have) creates _less_ reliability > than having it in the body. The mechanical retractable "A" pin on the "A" lenses has indeed caused more than its share of problems. Perhaps that's why Pentax chose to abandon that with the later auto-focus lenses and rely on electrical isolation instead (and now they've abandoned even that; the DA lenses can't ever be moved off the "A" position as there's nothing to move). -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
