I'm surprised the high iso performance is not better than 25k. D4 is 200K. D800 is similar but has higher pixel count. I would have expected 50K or a 100K max iso exposure. I wonder if iso 3200 or 6400 would be cleaner than the D800 or my D7000, given the larger photo site size.
"Cameras and lenses are simply tools to place our unique vision on film. Concentrate on equipment and you'll take technically good photographs. Concentrate on seeing the light's magic colors and your images will stir the soul." Jack Dykinga