TTL 3D Color Matrix Metering II metering with a 2,016 pixel RGB sensor
Auto modes (auto, auto [flash off]), Advanced Scene Modes (Portrait, Landscape, Sports, Close-up, Night Portrait), programmed auto with flexible program (P), shutter-priority auto (S), aperture-priority auto (A), manual (M), quiet (Q) and Effect mode.
Although the D7100 has 24.1MP, while the D7000 has only 16.2MP, there are no significant improvement for the newer ones. DxOMark say is "just a smidge better in all regards". The D7100 also removed the Optical Low Pass Filter (OLPF), but compared with Nikon D5200 which has same 24.1MP sensor and still has OLPF, the difference is insignificant.
The sensor of the D7100 uses Nikons DX format, resulting in a crop factor of 1.5x. Additionally the software allows to add a crop of another 1.3x (resulting in about 1.95x compared to 35mm). Selecting this additional crop mode allows faster focusing in video mode and also enables interlaced video recording modes.