it was near dusk at a local ski resort and i was trying to shoot some snowboarder doing tricks. 40d in manual model, iso 1600, fast shutter & spot metering. pics get kinda dark. i'd like to use faster shutter speed but everything would be black over 500. slower shutter speed and everything's blurred. aperture can only go to 4. any ideas? btw i follow the snowboarder as he moves. thanks.