I really need some advice shooting school basketball games. My photos are really grainy. I have a Nikon D7000 with a Sigma 70-200mm F2.8 lens. I am a novice at this. I have fiddled around with different settings to no avail. The photos I took yesterday had a shutter speed of 400 and ISO of 1600. I was using the Shutter mode. I also have the ISO sensitivity control off. I shoot in JPEG and have no desire to use RAW Can someone please advise me in layman's terms the settings I should use? I also have no idea which settings I should use on optical stabilizer on the lens. Any help would be appreciated. Thank you!