Nikon is serious about digital photography. Nikon's F-mount has been supported by digital systems since the release of Kodak's first digital camera in 1991. Nikon's partnership with Kodak continues to produce new models with the DCS 620 released this year, but reluctant to be beholden to the American film giant, Nikon has also released a series of cameras (the Nikon E series) with the Japanese film giant Fuji. Nikon's serious about digital photography, and after exploring different systems with Kodak and Fuji, they have decided to release an internally developed model based on their F5 film camera. Nikon introduces its "NEF" raw (unprocessed) format which provides colour information with 12-bits per pixel using lossless compression, but also provides the option to shoot straight to standard JPEG files if you need to hit a short deadline (although the latter sacrifices post processing control, like white balance adjustments).
The Nikon F5 was also the donor body for the Kodak DCS 620 (the Nikon E series uses the older F4 body), but physical similarities are less than you might expect. While the DCS cameras look like someone has welded digital components onto a film camera, the Nikon D1 is a much smaller, better coupled, variant that looks much more like a standard F5. This tighter integration not only results in a camera roughly 75% the weight of the DCS 620, but also allows for the D1 to maintain the same environmental sealing present in the F5.
Comparisons to the DCS 620 (rather than the E series) is natural, as both use a similar sized sensor resulting in a cropped field of view compared with 35mm film (and without the E-series' reduction optics system). The D1's Sony CCD is slightly larger physically (1.5x crop vs 1.6x) and with 2.6MP compared to the 2MP of the DCS 620. The D1 has an incredible 1/16,000 of a second shutter speed (and flash sync) by turning its sensor off faster than the mechanical shutter can close. It can shoot 4.5 frames per second for 21 consecutive shots, which while just better than half the physical limitations of the F5 body (8fps) is an improvement on the current digital best of 3.5fps for 12 frames by the DCS 620 and DCS 520. Perhaps the biggest difference between the two has nothing to do with technical merits, but the $5,500 price tag of the Nikon D1—half that of the DCS 620.