Holy crap! Now you can take a picture of your black cat at midnight in a dark closet!
The new EXPEED 4 image-processing engine, a new Nikon FX-format CMOS image sensor, and an effective pixel count of 16.2-million pixels enable capture of images that exhibit stunning sharpness, enhanced depth, and natural skin tones. A range of standard sensitivities from ISO 100 to ISO 25600 achieves images exhibiting sharper edges and smoother, more beautiful colors. The D4S also supports extended sensitivities as low as the equivalent of ISO 50 and as high as the equivalent of ISO 409600. What's more, the accuracy of auto white balance has been increased for clear color reproduction, even with shooting under difficult artificial lighting.
http://www.nikon.com/news/2014/0225_dslr_01.htm
The new EXPEED 4 image-processing engine, a new Nikon FX-format CMOS image sensor, and an effective pixel count of 16.2-million pixels enable capture of images that exhibit stunning sharpness, enhanced depth, and natural skin tones. A range of standard sensitivities from ISO 100 to ISO 25600 achieves images exhibiting sharper edges and smoother, more beautiful colors. The D4S also supports extended sensitivities as low as the equivalent of ISO 50 and as high as the equivalent of ISO 409600. What's more, the accuracy of auto white balance has been increased for clear color reproduction, even with shooting under difficult artificial lighting.
http://www.nikon.com/news/2014/0225_dslr_01.htm