That's why it's good to shoot with f2 or so :) sometimes when I need more depth of field, I'm horrified about dark spots here and there. I sometimes shoot a white wall with f16 to see my all dust specs. And sometimes I'm trying to clean the sensor and when I shoot again to see if the cleaning was ok, usually there is still always a couple of spots...and then I have to think that usually I can't see those spots if I'm not using f8 or so.