Canon | 70-200mm f/4.0L USM Autofocus Lens | 2578A002 | B&H Does anyone have this lens or have comments on it? I'm looking for a 70-300ish range lens that's fairly fast. I can't afford the f2.8 but it appears faster than the 70-300. Any thoughts? I'll be using the lens to capture fire scenes for the local fire department.