The Nikon D3S is a 12.1 megapixel professional-grade full frame (35mm) digital single-lens reflex camera (DSLR) announced by Nikon Corporation on 14 October 2009. The D3S is the fourth camera in Nikon's line to feature a full-frame sensor, following the D3, D700 and D3X. It is also Nikon's first full-frame camera to feature HD video recording. While it retains the same number of pixels as its predecessor, the imaging sensor has been completely redesigned. Nikon claims improved ultra-high image sensor sensitivity with up to ISO 102400, HD movie capability for extremely low-lit situations, image sensor cleaning, optimized workflow speed, improved autofocus and metering, enhanced built-in RAW processor, quiet shutter-release mode, up to 4,200 frames per battery charge and other changes compared with the D3. It was replaced by the D4 as Nikon's high speed flagship DSLR.
Full-Frame (36 mm × 24 mm) 12.1 megapixel sensor with ISO 200–12800 (ISO 100–102400 Boost) using reworked gapless microlenses
14-bit A/D conversion, 12 channel readout
Image sensor cleaning (dust removal with 4 frequencies)
Nine to eleven frames per second in continuous and FX/DX mode
Quiet shutter-release mode
Faster operation workflow
Automatic correction of lateral chromatic aberration for JPEGs. Correction-data is additionally stored in RAW-files and used by Nikon Capture NX, View NX and some other RAW tools.
Larger buffer for 48 RAW frames in one burst
Enhanced built-in RAW processing with extended Retouch menu for image processing without using a computer
720p/24 frames HD movie mode for extremely low-lit situations, 50/60 Hz flicker reduction, HDMI HD video output and stereo input (3.5-mm diameter) with optional manual sound level control. The Motion JPEG compression allows easy extraction of single frames afterwards as JPEG
Many independent reviews and comparisons show that image noise was improved up to 2 stops compared to the Nikon D3 or D700. Other functions, especially autofocus and speed, support this, causing PhotographyBlog to conclude: “hand-held photography anytime, anywhere, without flash”. There are comparisons with the Canon EOS-1D Mark IV, which is rated 1.3 stops lower by DxOMark on their low-light ISO score (1320 ISO vs. 3253 ISO for the D3s).
Low-noise videos are valuated useful. While not officially documented in user's manual, D3s indeed features the full manual control in D-Movie mode, including aperture, shutter speed and ISO. This feature was reported and posted by various users and eventually confirmed officially.
On 21 December 2009, Nikon announced  that NASA had purchased 11 D3s bodies and assorted lenses for use in the United States space program, including on the International Space Station. The D3s cameras are identical to the model sold to terrestrial users and will be used unmodified.
In April 2010, the D3S received a Technical Image Press Association (TIPA) 2010 Award in the category of "Best Digital SLR Professional". In August 2010, the European Imaging and Sound Association (EISA) presented the D3S with the European Professional Camera 2010-2011 award, citing high ISO sensitivity combined with low noise and a high level of detail.