Don't count out the D800 for low light. The comparisons done by Mansurovs shows that while the D3s is better at low light, the difference is only seen at the very highest of ISO's
See here -
[h=3]Compared to Nikon D3s[/h]
What about comparing the D800 to the low-light king, the Nikon D3s? Let’s take a look.
[h=3]25) Nikon D800 vs D3s ISO Comparison at low ISOs[/h]
Same deal with the D3s – it shows almost identical performance at low ISO levels:
[h=3]26) Nikon D800 vs D3s High ISO Comparison[/h]
Let’s see what happens when both are pushed to ISO 1600 and above:
Once again, ISO 1600 is very comparable.
And the same at ISO 3200.
At ISO 6400 the shadow area of the image on the D3s looks cleaner.
The same at ISO 12,800.
When pushed to ISO 25,600, the Nikon D3s is cleaner and retains colors, while the D800 still shows more details. D3s clearly retains more dynamic range at this ISO level.
[h=3]27) Nikon D800 vs D3s Summary[/h]
Unlike the Nikon D700, the D3s is a worthy competitor to the D800. At high ISO levels the Nikon D3s definitely shows better ISO performance in the shadows, mostly because of higher dynamic range. This is clearly visible at ISO levels 12,800 and 25,600. At the same time, the Nikon D800 still resolves more detail at high ISO levels, thanks to lots of resolution and the down-sampling process.
