I'm looking into buying a 70-200mm lens and have two picked out that I could probably afford. The first is Sigma's 70-200mm 1:2.8 EX DG Apo Macro HSM II. The other is Canon's 70-200mm f/4 "L" series lens. I love the canon lens but wonder if I wouldn't be just as happy with the Sigma (I have only used the canon lens for about 5 mins, and have only seen the Sigma online). Overall, I want the lens that will give me the sharpest picture. I take alot of family/couples and children pictures almost all photos are outdoors during the day so light isn't a big issue. I do like to take wildlife pictures so I would probably purchase an extender along with the lens.