Need help with new lens....canon T3 I've been viewing many of the discussion posts re: finding the "perfect" walk around lens for the canon dSLRs. I will be taking a trip to Europe in August and will be visitng all the fun tourist sites...Pompeii, Vatican, etc. I have the kits lens (18-55) and recently purchased the 50mm. I like both lenses but I am looking for a lens that will be as close to the jack of all trades as I can get. My photography instructor suggested the Sigma 18-200 or Canon 18-135. Would one of these work for a good all-around travel lens or is there any others I should be considering? Any help would be greatly appreciated!!!