A 24.1-million-pixel, APS-C sensor with no anti-aliasing filter should ensure large and sharp images from Nikon's new enthusiast-level DSLR, but there's a lot more to the D7100 than that. Read the Nikon D7100 review...
Nikon D7100 review – Autofocus
Like Nikon’s professional-level D800 and D4, the D7100 uses a 51-point AF system, which means it is a capable performer when shooting high-speed action. Fifteen of the central AF points are the more sensitive cross-type. In fact, in the 1.3x crop mode, all 51 points cover virtually the entire frame. Nikon claims that some of the AF points are sensitive down to f/8, which means they are just as responsive with a lens closed down to this aperture setting or with a 2x teleconverter mounted to an f/4 lens. I used the camera with the FX-format AF-S Nikkor 70-200mm f/4G ED VR lens (105-300mm equivalent), which becomes a 210-600mm optic with a 2x converter, and the camera’s AF points proved to be just as effective.
AF modes are selected via the focus mode selector, which is located next to the lens mount and also features the AF/MF switch. Focus can be switched between single, nine-point, 21-point, 51-point and 3D tracking. In each mode, single, continuous or auto AF can be used, the latter of which automatically switches between single and continuous, depending on the subject, making it perfectly suitable for everyday use. Even in low-light conditions, the AF system of the D7100 is, once again, perfectly capable. Nikon states it can focus down to -2EV (moonlight), and although AF is not as responsive under such conditions, it is possible to get sharp focus while failure to focus at all is unusual.