After not using the lens for a while, I take it out of it's bag, and connect it to the camera, and it won't auto focus. I turn the focus ring back and forth a bit, and then try auto focus, and it does so grudgingly, and intermittently. I have to operate the auto focus repeatedly until finally it starts working reliably. It behaves as if the SDM motors are "frozen" and have to be worked in a bit before they start responding.
This happens every time I put on the lens and it has been sitting for more than a few days. To head off the inevitable questions, here are some conditions:
-The lens is always stored in its bag, indoors, in an air-conditioned room.
-It has never been damaged or even bumped.
-The contacts are very clean.
-It does this on the k20d
-No other lens I own has AF problems. Only the SDM on the DA* 50-135.
-I have the latest k20d v1.03 firmware
-The lens is attached properly
I guess I am just not meant to have an operable DA* lens. First 3 defective DA* 16-50's and now this!
Last edited by PentaxPoke; 04-29-2009 at 06:53 PM.