> That "--" readout is normal. What is slightingly referred to as the > "crippled K-mount" on all the DSLRs doesn't have the aperture follower > linkage, so there is no way for the body to know what the aperture ring > on the lens is set to (other than the separate "A" position detection). > > It still sounds to me like a purely mechanical problem. > > Normally, when a lens is off the camera, it will be stopped down to > the aperture set on the aperture ring (or f/32 for the "A" position). > As you rotate the lens while mounting it on your camera the mechanical > aperture linkage between the body and the lens is supposed to engage, > and this will open the iris up to maximum aperture. > > It sounds to me as though this is not happening when you have the > lens set to "A". If (after the lens is mounted on the body) you > then turn the aperture ring to f/2.8 and back to "A" again this > will give the two parts of the mechanical linkage another chance > to mate properly. It sounds as though doing this is enough to > get your lens working correctly again. > > Take a look at the aperture linkage on your lens, and compare it > to the lever on any other lens. It should stick straight out > parallel to the axis of the lens. If the tip of the lever (the > part that sticks out the furthest) is bent inwards towards the > axis of the lens it's possible that the very slight flex in the > lens that you introduce while mounting it causes it to just miss > engaging with the body (or, alternatively, it's possible that > the lens itself tilts the lever slightly when the aperture ring > is all the way round to the "A" position). Turning the lens > aperture ring to f/2.8 after the lens is mounted forces the link > back to the correct side of the body coupler, whereupon normal > operation should resume. > > If the lens always works normally if you have the aperture set > to f/2.8 when you mount it I'd suggest simply doing that, and > only turning the aperture ring to "A" after the lens is mounted. > > Failing that, I'd consider trying to bend that lever very slightly > so that the tip of it moved fractionally further away from the > axis of the lens, but I'd only do that if the workaround failed. > > Has the lens ever been dropped, as far as you know? That can > bend that lever if you're unlucky enough to have that be the > first part of the lens to come into contact with something hard > (and that will push the tip of the lever towards the lens axis).
Thanks John. That was useful and instructional as well. As far as I know, no, it hasn't been dropped. I've had it since 98/99 though. I'm thinking your analysis is right on. I sense a very slight 'binding', when I mount/dismount the lens. Tom C. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
