I am new to photography. I have looked over a number of the useful threads and have been trying to shoot gymnastics (poor lighting, action photos, no flash). Most of my images come out dark or with blurred feet. I usually bump up the ISO to 800 or 1600 and shoot shutter mode. From what I read here, it sounds as if I need a different lens, perhaps 80-200 f-2.8, or something of that nature. Any recommendations, how do I know what will be compatible with my camera body and also the Sony alpha 100 that has image stabilization in its camera body. I don't want to buy something too expensive but would like to shoot better photos.