Newbie questions

[antigravity]

I just wanted to ask about what I'm supposed to look out for when buying glass.. For example, I know that the f/XXX value on the lens is the size of the aperture, but what does this do for my pictures? Also, what is the difference of the L lenses? :D Forgive me if the questions seem ignorant, he he.. I just didn't want to assume anything.. thanks! :D

Oh! And I'm thinking of buying an EF 100-400mm f/4.5-5.6L IS USM (http://www.supereastasia.com/prod_details.asp?id=5&subid=20&pid=99).. would it be better for me to get an EF 70-200mm f/2.8L IS USM (http://www.supereastasia.com/prod_details.asp?id=5&subid=20&pid=89) in terms of overall value? :confused:

[tim]

I'd recommend taking a basic photography class before you start buying lenses. What you learn there, plus experience with whatever lens you already have, means you'll be able to make informed decisions. If you're in a real hurry read this thread (http://photography-on-the.net/forum/showthread.php?t=56752).

[antigravity]

thanks! :D