Originally posted by kiwi_jono So if you look at a subject using live view (ideally with with magnification) and turn the manual focus ring, you don't see focus change at all? If so that sounds like a mechanical problem in the lens.
Hi Kiwi, the lens focussing problem occurred when I was using the viewfinder, I seldom use Liveview because in bright conditions it is difficult to see the picture. I tried using Liveview as you suggested and I still had the same problem. However, when I tried to focus I detected the camera give a double shake as if it was trying to focus, but nothing happened. I have concluded that the lens has an electro-mechanical problem and I am trying to decide if it's worth repairing. I own a Tamron 28-300mm lens and a Pentax 18-250mm lens. A comparison showed that they are just as sharp as the 18-135. Maybe I'll use one of these as my standard lens. They are a bit heavier but that's OK.