Just moments after the Nikon D5 rolled into our office we whisked it into our studio, putting the flagship FX-format DSLR in front of our test scene. We were curious to see exactly what the 20.8MP CMOS sensor is capable of, and what its impressive ISO range looks like - especially its astronomical ISO sensitivity limit of ISO 3.3 million. And we couldn't resist sharing some initial thoughts with you.

So what does ISO 3 million look like? See for yourself if any of the ISOs above the D4S' previous maximum ISO offer anything useful. Nikon's claims of better ISO performance due to color filter array optimizations appear to have some merit: noise levels in Raw mode are slightly lower in comparison to the D4S, or any other camera, when normalized. Although the performance advantage is more obvious at higher ISOs, like 204,800, the actual benefit does appear to be minimal at best. In fact, compared to the 42MP Sony a7R II, midtone performance at the very high ISOs is fairly similar at a common viewing size, with benefits most apparent in high ISO dynamic range, or, shadow performance at in extremely low light scenes. That benefit on the high ISO end diminishes at lower ISOs: the D5 has a 2 EV deficit in base ISO dynamic range compared to the a7R II, according to our very own DPReview forum member Bill Claff's independent measurements.A big difference between the two cameras is that the Nikon can shoot at 14 fps, so it's possible that this lower dynamic range at low ISOs is a side-effect of the D5's rapid sensor read-out architecture.

Why the lack of a drastic improvement in high ISO performance? At this point, we're simply running up against the best that modern silicon can do: with single electron read noise levels at the highest ISOs in some modern architectures, there's only so much performance to be gained without drastically increasing conversion efficiency or light gathering capability past the limits already imposed by the Bayer array and current (very good) microlens design.

When it comes to JPEG, Nikon (and Canon, for that matter) have some work to do with respect to optimally balancing sharpening and noise reduction in JPEG, as detail in the Raw is left on the table at both low and high ISO sensitivities compared to Sony's more sophisticated engine. Colors generally appear punchier than its predecessor, with some of the nicest yellows we've ever seen (Sony's yellows look green in comparison). Color saturation is retained at high ISOs even if detail isn't.

There's a lot more testing to do. Rest assured we'll be doing much out-of-studio shooting in the weeks to come - putting to test what we initially feel is the most exciting AF system we've ever seen in a DSLR to-date - but for now see how the D5 performs in our standard studio scene test.

* Interestingly, a sinusoidal dynamic range vs. ISO curve is reminiscent of older Canon designs (like the 5D Mark III), distinctly different from the performance of Nikon (and Sony, and even recent Canon) cameras we've come to expect (note the D810's rather linear drop with ISO). In Canon's older designs, this was due to a dual amplification architecture - which was far from ideal when it came to dynamic range - and we're surprised to see this result in the D5, as it means that intermediate ISOs on the lower end are less than ideal. We'll be following up on this result in our dynamic range tests to visualize the noise impact.