I'm making a little money from a recent gig and want to add to my equipment. I'm considering buying a low light lens, but am not sure what to get. I have a Canon 40D and would use it for shooting concerts. If I got a light meter, I could use it for just about everything - I do a lot of product and portrait work as well. Problem is, I don't make money shooting concerts, but they're more fun. I make money shooting portraits and product, so the investment would aid my business. *sigh* What are some good, general purpose, low light lenses for Canon D-SLRs? BTW, (this is a dumb question) can you use SLR lenses on DSLR cameras? I never thought about it until now.