Hi, there seems to be something wrong with my Sigma 70-200mm OS HSM. When I focus on my subject, by half pressing the shutter button, as the picture comes in to focus, it starts to moves half way down the view finder, once focus is found, the picture jumps back up to be viewed in the entire view finder. I have had this lens for 6 months now. My issue is now, it's my nephew has a event coming up and there is not enough time to have the lens returned from being fixed before the event. By using the lens, as it is, will I cause more mechanical damage to it or will it stop working on the day? I expect to take around 300 - 500 shots.
