18:135 smc da won't autofocus for K20d

In autofocus mode my new 18:135 smc da lense will not always focus when I try to depress the button half way on my K20d. The focus indicator keeps flashing. To take a picture I have to put the camera in manual focus mode. Anybody have this problem and a solution?

I had a similar problem once or twice with my K5 and the 55-300 just after I bought the camera. The camera would focus on a contrasty subject on which you would have thought that it would have found focussing easy. However, the focus indicator continued to flash and the shutter refused to fire. I resolved it by focussing on a much blander subject the same distance away, or switching to continuous focussing where practical.

I have not had that problem since, although I have not used that camera/lens comination recently. I would be very interested if anyone can pinpoint the cause.

John

AF is not perfect and there are subjects that fool it. In those circumstances, I focus on something else at the same distance, maybe use Quick Shift or indeed switch to manual focus.