Nikon 51 focus point AF system is powered by Multi-CAM 3500FX autofocus sensor module for faster, more accurate autofocusing. 51 focus points are fully active when lenses with a maximum aperture of up to f/5.6 are used, 15 focus points at the center of the frame are cross-type sensors that detect phase differences both horizontally and vertically, 11 focus points (five at center with an additional three to each side) are fully functional when lenses with a maximum aperture of f/8 are used.