Hey all, I have a Rebel XTi (EOS 400D.) Right now I am just using the kit lens, and would like to upgrade. I would like a lens that could do well in lower-light conditions. Also, I would be doing portriats. My budget is around $300. I've been looking at the Canon EF 28-135mm, but I'm reading that it's better to get EF-S lenses. Anyone have some recommendations? I'm not very camera savvy. Thanks!