I have tried without filter but to no avail. Still auto focusing above 35mm but not between 18mm and around 35mm. This has got me stumped.

Hi, thanks for the reply.
The only filter in use is a UV filter mainly for front element protection

Dave

I recently acquired a 18 - 135mm Pentax lens as a walk about lens. There seems to be a problem with the AF It won't auto focus when used between 18 and 35mm. Above that it is fine. I have two K5 bodies and it has the same problem with both bodies so I have to assume that the lens is at fault. I have no problem with manual focus only when set on AF and only between 18mm and around 35mm. Has anyone else encountered this problem?

Cheers Dave