Hello Everyone I was just wondering what would be better. To get the 100-400 from Canon or to use the Canon 70-200 with an extender. I havent been able to test any of these lenses but I know that I would not stand the 100-400 push pull zoom. Most people say that using an extender makes IQ horrible. Also what about the Tamron or sigma 70-200. I will be using this for pictures in the Zoo and Portraits. I am using the Canon 40d. Feel free to put in photos!!