Looking to get the Nikon 70 - 200mm for sports photography. Is 70 - 200 f4 fast (and sharp) enough for sports photography? Under stadium lighting, it may be a challenge for the f4, what about in daylight on a field? I would like to take base ball game, where the speed of the ball is so fast after the hit, compare with soccer. Reach is not an issue as I can crop it.