I am still somewhat new to photography, and I am saving to upgrade my S3 IS to an EOS 40D. My parents have an old kit lens from their film rebel I am going to use, but besides that what lenses should I buy right when I get my camera? I want a lens to get me up close to the aircraft for airshows, (I go to airshows often) and I was thinking of buying the 1.8/50mm lens that everyone always talks about. But how can you tell a good lens from a bad one? Can someone guide me to the right first lens(es) with my new DSLR? I pretty much photograph everything around me that's interesting. Thanks!