I have a 7D that I do most of my photography with currently and I'm after an L series wide angle zoom lens that will be suited to motocross, motorsports and some portraiture I do from time to time. I wanted to use something fast - like f2.8 but wasn't sure how maybe f4.0 would look on a cropped frame camera in like a 17-40mm. I love the look and feel of a 16-35mm f2.8 and when I graduate to a full frame I will be able to get the most out of it but could anyone shed some light on this for me as which lens might suit me best. I know the 17-40mm is much cheaper....would it be better suited than the 16-35mm? Any help with this would be greatly appreciated