The Nikon D850 will replace the D810 which already ruled the high-resolution lineup for three years.
The Nikon D850 has a 45.7MP FX (full frame) BSI CMOS sensor without a low-pass filter, the first backside-illuminated sensor in Nikon's lineup, can capture 7 frames a second stills (8fps with the new MB-D18 grip) and has a base ISO of 64 and tops out at ISO 25,600, natively.
The D850 shares the EXPEED 5 plus also the 153-point focusing system of the Nikon D5, which has 99 cross type sensors (15 of which can focus at f/8).
The Nikon D850 captures 4K video at 30/25/24p and uses the entire sensor surface (unlike the bigger Nikon D5 which has a 1.5x crop when shooting 4K video). This is the first time on a Nikon DSLR that there are zebras and focus peaking, though that works only for 1080p. The D850 can capture slow motion at up to 120p in FullHD. There's also 4K timelapse in camera and up to 8K timelapse through the built-in intervalometer.
The back side of the Nikon D850 has a tilting LCD touchscreen which supports Touch AF in Live View. There's also Silent Photography in Live View that is able to shoot 6 fps at full resolution without the mechanical shutter noise.
The Nikon D850 can capture 51 14-bit RAW files before its buffer is filled - twice as many shots as the D810. Those shots are recorded to the fast XQD card in the first slot, while a second SD slot can be used for overflow or backup.
The battery is the EN-EL15a – is a more powerful version of the Nikon's popular battery, that claims 1800 shots battery life and 70 hours of video. The Nikon D850 is compatible with the old EN-EL15 battery too.
There is Wi-Fi as well as Bluetooth, which is used in conjunction with Nikon's SnapBridge app to transfer images to your smartphone when you are shooting.