I did some fiddling today with an old K2 and my girlfriend's *ist D to figure out how far you can mount the lenses without engaging the holds-aperture-open lever. This isn't exactly a new trick for me as I used to do it with my ME Supers to get depth-of-field preview before I got Super Programs.
On the *ist D, the magic point appears to be found by turning the lens until the white perloid hemisphere on a K/M lens lines up with the line formed by the edge of that scoopy cutout on the handgrip side of the lens mount. I haven't yet actually shot pictures with the lens mounted like this to confirm that you get accurate stop-down metering in Av mode. DJE
