Getting autofocus right - Part 3

It can be frustrating and dispiriting when you can't rely on your camera and lens to focus accurately every time you take a shot. And it's often difficult to track down the source of the problem; so many variables have to be considered and it can take time and effort to find and fix them. In this feature we'll outline some of the main reasons your camera and lens might be unable to focus precisely.

Regardless of the conditions in which focusing fails, it's always best to do the simplest, cheapest things first. Switch off the camera then detach and re-fit the lens. Turn the camera on and see whether the problem persists. Power-down the camera again and remove and replace