Nikon has now officially unveiled the D7100 which will succeed (but not replace) the D7000 DSLR. The main improvements are in the areas of sensor resolution and the number of autofocus points. The film mode has also been improved, and the low-pass filter has been removed from the sensor.
Despite what some were secretly hoping in the run-up to the Nikon announcement, it's not a successor of the D300S, but an upgrade of the D7000. The interface has remained intact for the most part. The size of the sensor is 1.5x that of its predecessor. Nikon is positioning the D7100 between the D7000 and the D600, so the D7000 will remain available.
The sensor has a resolution of 24.1 megapixels and Nikon claims it's not the same sensor as in the D3200 or the D5200. While the ISO range has remained the same (100 - 6400), Nikon says it has been improved in quality compared to the D7000. The Hi 1 and Hi 2 settings are also present.
The low-pass filter on the sensor has been removed, which was also done with the D800E. This filter removes moiré, an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh. The drawback of such a filter is that you lose some detail. This means that the D7100 should be able to take sharper images, and Nikon indicates that the higher resolution causes moiré to be barely visible even without the filter. Moiré can be removed with software as well.
The autofocus system has been expanded to 51 focus points with 15 cross-type autofocus points in the middle. This sensor is called the Multicam 3500DX, and it supports lenses with an aperture of up to f/8. The autofocus sensor is assisted by a Scene Recognition System RGB sensor with 2016 pixels for measuring the light. The contrast autofocus detection during live-view and filming has been improved for better accuracy and speed. The D7100 can take 6 frames per second in JPG and 12-bit RAW, 5 fps in 14-bit RAW and 7 fps with the 1.3x crop mode. This is made possible by the Expeed-3 image processor. The fastest shutter speed is 1/8000.
The display on the Nikon D7100 is slightly larger than that of the D7000, with a size of 3.2 inches and 1,228,800 dots or subpixels. The actual resolution is 640x480, or 307,200 pixels. It has extra white subpixels in addition to the standard RGB subpixels. This 'White Magic' technology comes from Sony which used it in its RX100 compact camera. It reportedly makes the brightness of the display twice as high, and the contrast of 1000:1 is equal to that of the D7000. It's unclear whether it's possible to adjust the aperture in the live-view mode, on the D7000 it was not possible at least. An extra spot white balance has been added, which speeds up setting the white balance in live view. The menu also has a new look compared to the D7000.
The body of the Nikon D7100 is still made out of magnesium and its 675g is somewhat lighter than the D7000's 690g. It's also dust and splash resistant. The design is somewhat more rounded than that of the D7000, and is therefore more in line with recent Nikon cameras like the D5200. The rest of this preview you can read on Hardware.Info.