I'm needing experienced advice. I'd like to get into shooting some football this season. Which would you buy? 1.4x Tele = 98mm-280mm (f/4) 2.x Tele = 140mm-400mm (f/5.6) The 1.4x just seems a bit short, but I've never shot on the sidelines, maybe it's the perfect length. What do you think? I like the fact that it'll put me at f/4.