When TechRadar attended the launch of the D3s, it was easy to scoff at marketing claims that the camera could "shoot in the dark", but a bit of experimentation reveals that at its highest ISO, the camera can amplify light much better than the human eye.
There's plenty of wow-factor to be had in pointing the camera at a totally dark room and then marvelling at the amount of detail returned from a fast shutter speed.
The highest ISO will be a gimmick most of the time - times when you really are shooting in the dark are likely to be few and far between, and the image quality of 102,400 is pretty crummy - our test pics were extremely noisy and suffered from heat spots and colour shifts.
But in an emergency, or when the content of a shot means more than the quality, it's useful to have a camera that will return intelligible images. It also means you never need to worry about the quantity of light, as you almost always have enough to return a usable shutter speed.
But while the 102,400 ISO is a headline feature, the real draw is the D3s's performance a few stops down the line.
We're used to Nikon's FX cameras performing well at high ISOs - the D700 is excellent up to ISO 3200 - but the D3s fairly blew our socks off. It's at least a stop better than the D700, with noise only just creeping into our test shots at ISO 3200, and not becoming a cause for alarm until ISO 25,600.
And, while the continuous mode isn't any faster, Nikon's claim that the D3s's buffer is more than twice that of the D3's is accurate - in 12-bit RAW mode we captured 36 frames at 9fps before the D3s paused for breath.
You get two continuous-shooting modes - the slower mode can be set from 1fps to 9fps, while the sportier mode goes to 11fps, although anything faster than 9fps requires you to crop the active area of the sensor down to the equivalent of the D300s's.
It's here that the Canon 1D MKIV - on paper - has a 10 per cent speed advantage, as it goes to 10fps with its APS-H sensor. The rest of the D3s's performance is beyond reproach, as it should be. There's no shutter lag to speak of and no sense of delay as you flick through shutter speeds or aperture sizes.