I have a nikon d200 with the 18-105mm f3.5-5.6 lens and i wanna shoot my friends playing basketball but f3.5 is just not big enough for indoor basketball. i would have to use ISO hi1.0 in order to shoot but the pictures come out tooooooo grainy. with that said, im looking into prime lens' because i dont have enough money for a zoom lens with f2.8. im willing to buy nikon or off brand lens. any advice on what to buy?