ISO 6400 + Topaz De-Noise 5
Note that the following set of images may have been taken at high ISO and then edited. I think that posting RAW images are a decent way of comparing sensors, however, I feel that using RAW images for comparison is not real world and not a valid way of comparing sensors. Rather, I'm posting EDITED photos to show you how the camera produces images in the real world. If the camera, like this D800, has such high resolution that noise recognition algorithms work better, I think that's a good thing to know and see. This photo here is a great example -- this is ISO 6400 but Topaz De-Noise 5 did a great job getting rid of a lot of the noise!