[Joe]

Trevor,
I've attached a few pictures I took last saturday, to try and illustrate my suggestions.

The first one was taken as a penalty was taken. It gave me time to prefocus (exactly as Rudra suggests above) on the ball, and frame the shot ready for the player to run into shot and kick it. Bonus is you know the ball is going to be sharp, but watch out for the players 'kicking' leg...that's gonna be the first thing to go blurry. Set piece moves where you know that the ball and/or players are going to be in a set place really helps increase the chances of getting sharp images......Rugby Union is a much easier field sport to photograph in this respect! American football is a sport I've not but I'd love to photograph because of this too.

The second illustrates my point about filling the frame with action. I took this as action got quick close to me. It can be a bit hit and miss regards the framing and crop, so have your motor set to continuous shooting. Would also say take plenty of shots, as the chances are the action you see in the viewfinder has already been and gone by the time the camera mirror flips up and shutter opens!....try and press the shutter release slightly before the action happens (sounds mystic, but gets easier with practice).

The third shot shows what you'll probably be getting as the light goes and the floodlights switch on. Shadows get harsher, light isn't as bright, and shots get more 'grain'/noise on them. I've tried to reduce this on neat image program (photoshop has a similar 'filters' function), but the tendency is for everything to go a bit smudgy and soft if it's filtered too much (I'm guilty as charged!) notice also, the ball getting abit blurry, a result of slowing down the shutter speed due to poor light levels.


I hope this helps?

cheers
Joe