The Nikon D800/D810 is capable of producing the following uncompressed video output: 4:2:2 8-bit 1080p Uncompressed Video – Although the video stream coming out of the HDMI port on the D800 is called “uncompressed” by Nikon, it does in fact use a form of chroma subsampling, reducing the total colors output from the better 4:4:4 format to 4:2:2. This is not so much a compression of the video stream as it is a compression of the number of colors in the video stream. This chrominance compression is similar to how a JPEG image compresses the color range and is quite effective, even for serious commercial use. The container format is controlled by the recording device for this video type…The 4:2:2 format produces smaller files that are visually equivalent in quality to 4:4:4.
So, in a nutshell, utilizing a Atomos Ninja 2 or equivalent device to record your camera HDMI output will not yield any significant advantage, unless we begin to witness the availability of true 10-bit 4:2:2 from future Nikon cameras.
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