I'm looking for advice on a wide angle zoom lens that would be good for waterfall and landscape photographs. Currently I have a Canon Rebel T2 film camera, but there's a good chance that I shall be going digital in the near future with a full-frame Canon D6. I only have 2 lenses right now: Canon EF 50mm 1.4 USM prime and Canon EF 28-135mm 3.5-5.6 IS USM zoom. I don't think that the 28-135mm zoom lens that I currently have is the quality that I want as well as I might need something a bit wider for some of the waterfalls. I am prepared to spend anywhere from $500 to $750, but I just want to make sure that it's a good (not mediocre) lens. I do want to stick with Canon lenses.