The low light scene is shot with Auto White Balance, to show how the camera's JPEGs look under artificial light. Any 'keep warm tone' options are left at their default setting.
The low light scene Raws are processed to demonstrate the capability of cameras in low-light shooting situations. Noise reduction is minimized and the white balance is neutralized to reveal blue channel noise. The black level is lifted to prevent noise being hidden by clipping. A standardized amount of sharpening is applied in Photoshop.
Under the tungsten lighting of our low-light scene the D610's auto white balance neutralizes most of the yellow cast, but still leaves a slight yellow tone across the scene. Moving up to ISO 800, you can see some color noise starting to creep into the JPEG. By ISO 6400 color noise is definitely noticeable in the D610, whereas the Canon EOS 6D appears smoother. This is in part to Canon's JPEG engine applying more noise reduction at high ISOs.
In terms of skin tones, the D610's auto white balance system still renders toward the warm (orange) side when compared to the Sony Alpha 7. Shooting in Raw or setting a custom white balance is still the best way to ensure accurate skin tones for portraits.
Comparing the D610's Raw images to other full-frame cameras, low luminance noise and high detail are seen at low to middle sensitivities. At ISO 3200 some slight color noise creeps in but fine detail is still visible. By ISO 6400, fine detail is starting to be sacrificed and color noise is more obvious, but not objectionable. Noise is on par with the EOS 6D and slightly less than the Alpha 7 - especially when compared at a common output size. By ISO 25600, detail is lost and color noise is apparent, and the D610 is still controlling noise better than the Alpha 7, but as well as the EOS 6D.