Ok I am going to buy a lens. Either the Canon 17-55mm 2.8 IS or the Tamron SP AF 17-50mm f2.8 XR DI II (IF). Which one would you reccomed??? Will the IS help that much more in a Wedding?? The main reason I am thinking about the Tamron is because that the Canon has been know for getting dust in the lens and I am worried about that. I mean to spend $1200 on a lens that gets dust in it, or is it worth it???? Please help!!!!