Just like many other Pentax-DA* 50-135mm users out there, I have the SDM issue where the lens will no longer auto focus. While possible to repair yourself (not recommended) I have found a simple work-around that seems to get the lens working. If you listen carefully (ear to the lens body) when you depress the shutter you will hear a high-pitch sound. If you keep pressing the shutter (triggering the auto focus), you may notice the pitch getting higher and higher. I have found after about 15 times, the lens will start to auto focus again. Depending on how much you then use the lens your mileage will vary.