I have taken many outdoor action shots (cycles, quads, bikes, etc) which turned out great, but I am having a hard time getting good shots at my sons basketball game. I use the action setting, but there are so many little bodies moving so fast, I am having a hard time getting a non-blurry shot. I tried the shutter priority (which goes as high as 1/16000), but when I get past about 1/250, my picture get too dark (what causes this?). So how do I use a high shutter speed (1/500 - 1/1000) on shutter priority, and not have the screen dark? This may be a stupid question, but this is about the only type of photography in which I have not been able to get satisfactory results. I appreciate any insight.