I bought an Olympus Evolt E-500 DSLR four years ago when it was already an outdated product for four years. So I'm cheap.
Lately, the camera has had an awfully hard time auto-focusing. It searched back and forth for the right setting but in the end, it gave up and stopped at some incorrect distance. Not all the time, just most times. The 40-150mm zoom was particularly bad at the 150mm end. As you can imagine, makes it hard to get that one-in-a-million shot possible.
I could override this focus problem with manual adjustment of the lens, but the E-500's viewfinder screen lacks crosshairs to guide you and the view is decidedly small and somewhat dim just to add to the frustration. Besides, it's an auto-focus camera for cryin' out loud.
My first thought for an attempted self-repair went to the electrical contacts between the camera body and the lens. I gently rubbed all the gold-colored contacts with a clean pencil eraser. I always try that first before applying chemical cleaners on contacts. The cleaning seemed to help somewhat, but the problem re-occurred in full flower quickly.
I was about to ditch my Olympus when I did a search for the experiences of similar folks. I came across a post on a forum that claimed a sensor cleaning would help. They said that using a Rocket-type sensor air blower was all that was needed. Their theory was that some dust had settled on the focus sensor and was throwing off the reading.
Wait, what?All it needed was some dusting?
Sounded too good to be true. But since it was free to do (told you I'm cheap) I decided it couldn't hurt to try.
So I took off the lens and held the camera upside-down while I blew out the mirror chamber and shunted some air under the mirror itself to stir any dust loose on the sensor(s). The poster recommended slight dusting pressure, but my Midwestern farm machinery ethic demanded that I employ gale wind forces on the E-500. To my credit, I did not even think about using my air compressor.
It worked. Both lenses now focus quickly and surely. Well, new-ish.
I love it when problems are solved with simple solutions. I don't know if such a sensor cleaning process would work on focus problems for other DSLRs by other brands. Thought I'd pass this little tip on to you for what it's worth.