Why is it the last? Are Sigmas horrible these days? 20 years ago, I shot some nice stuff with one on an old Minolta. You mean large aperture(which means low f-stop) or a "fast" lens. With both lens caps off, hold it towards a light and cycle it from f2.8 to 22. 22 is the smallest, 2.8 the largest. Aperture literally means "opening". A fast lens has little benefit on a bluebird or otherwise bright day. It will help on a low light situation when you have a poor ccd(or slow film).
Any focal length less than 28mm(maybe 26) and you start getting fish-eye(which might be desired).
Sorry I had my terms switched. You are correct.
Not that it is used much in mountain action type shots, but the LARGE aperture can give you great DOF shots that I really enjoy. Ill admit however that they dont get used much in snowboarding.
I wasn't saying Sigmas were horrible. I was specifically referring to the lens itself not the brand. The 70-200mm I just find too much. I'd rather something in a 24-105mm (be it a fixed 50mm or whatever).
At the end of the day, a lens choice can be pretty personal. PHOTOGRAPHS (not "pictures") are very much a form of art, and while I prefer a some art, others may not. Eek, Fuzebox and I might all prefer different styles and therefore prefer using very different lens. I dont think you have gotten any bad advice here and have been given some great options to try out.
Have fun and see what you like. (or post them here and we will judge)
Gotta throw it out there again though. The 50mm 1.8 is a great buy for a lens that you can do a lot of fun with. I highly recommend that for any new photographer.