> > > > Has anyone else had issues with adaptall lenses set on "A" working > > accurately with program and shutter-priority modes on Pentax cameras? > > I just plain and simply have problems with Pentax cameras giving accurate > exposures in automatic. I don't know why. > Just lucky, I guess.
Given my normal subjects, I probably shoot 90% of my shots in shutter priority. Back when the Tamron 300 was my preferred lens I was using it that way on the PZ-1p with a PK-A adapter (specifically purchased to replace a PK adapter so that I would be able to use shutter priority), and the only problems that I can recall were caused by mechanical mis-assembly on my part; as has been mentioned it's a little tricky getting the tabs on the adapter to mate with the lens, especially if you're also using one of the matched Tamron teleconverters. Mind you in those days I was shooting mainly Royal Gold 100, which is quite forgiving. I could have missed cases where the exposure was only off by one stop. That means I may not have spotted errors in head-on shots exposed at 1/1000s (where the lens only closed down by at most one stop), but I would not have expected to miss exposure errors in pan shots (most taken at 1/180). Nowadays I mostly shoot Provia 100F (nowhere near as forgiving), but I'm still mainly using shutter priority. No problems from either the PZ-1p or the MZ-S. I do have one suggestion, though. The "A" contact detector is extremely touchy. Sometimes, if I stress the lens mount exactly the wrong way when holding the camera, I can flex things enough that the pin fails to make contact. (This is more likely to happen if I've got the Sigma 1.4x TC mounted, but I can cause this error with nothing but a Pentax lens). This can cause disastrous errors in exposure, because suddenly the body thinks this is a "K" lens set to f32. This results in gross underexposure if I've manually selected the shutter speed, or horrendously long exposures if I'd left the camera set on auto. Of course if you hear a 1/4 sec exposure where you were expecting something a lot faster you immediately check the camera settings. But doing this usually causes you to shift your grip slightly, so everything *appears* to be fine. Try flexing your lens/body combination by pushing up on the lens (a normal sort of grip when hand-holding a medium telephoto) with the lens set on "A", and see if you can get the aperture readout to flicker to f32.
