I'm going away on a trip into some scenic (big mountains, plains, etc.) places and want to buy a wide angle lens before I go. I own a 50D so I know there'll be the 1.6x crop limiting how wide I can go, but really want some advice on what lens I should get. Budget is probably around US$1,000 (or more if there are gems that are worth it) Currently thinking of the following. Any recommendations? 1. EF 16-35mm f/2.8L II USM 2. EF-S 10-22mm f/3.5-4.5 USM 3. EF 17-40mm f/4L USM Why is the 16-35 twice as expensive as the other two? Because of the f2.8? Is it worth it if I'm going to be shooting daytime big scenery mostly? Thanks!