The Nikon D40X starts at ISO100. The Nikon D90 starts at ISO200. Which starting point is better, ISO100 or ISO200? I'm willing to sell my Nikon D40X and buy a D90. I need the built-in focus motor for the 50mm f/1.8 lens. I heard the D90 uses a CMOS sensor. Is it as good as a CDD sensor (D40X) in terms of quality? Thanks!