For the last couple of days, I've been looking at adding to the lens I already have. So far I've come up with Canon EF 70-200 f/4L and the Canon EF 50mm f/1.8 II. Can anyone that used these lenses give any advice? I want to get a Telephoto lens and I heard the 50mm f/1.8 is a reliable lens, tho I heard the latter is built "cheaply." If that was the case, should I go with the 50mm f/1.4? As you can see from my sifnature, I currently use a 28-105mm f/3.5-4.5 lens. Would the other two lenses complement the existing one?