Built for pixel power, not for speed
Nikon kept the same 51-point autofocus system with 3D focus tracking in the D3X that it used in the D3, D300, and D700. And in our tests, we saw very similar down the lights, the D3X's AF prowess really emerged. Even at our test's dimmest setting of EV -2 (about the brightness of a scene under a full moon), the D3X focused in less than 1 second.
Nikon also kept the same excellent 1,005-pixel 3D Color Matrix II metering system, which works with the AF system to help in tracking subjects during in the camera's continuous AF tracking modes. You can choose from Matrix (Nikon's version of evaluative), centerweighted, or spotmetering. The latter grants you a tight spot of about 1.5 percent in the center of the frame. (The Canon offers a wider 2.4 percent spot.)
We found Nikon's Matrix metering effective in determining the best exposure for a given scene. The system compares the current scene with a database of images in the camera to determine, for instance, if you're shooting a portrait, or if the scene is backlit, or if the exposure should be something other than the standard reading. It generally works well. There will always be situations in which you'll want to use exposure compensation, but more often than not, over a wide variety of shooting conditions, Matrix metering makes the right decisions.
BODY DESIGN AND BUILD
Like Canon's 1Ds Mark III, the Nikon D3X has a rugged body made of magnesium alloy with weathersealing to withstand rough shooting environments. Since the body is nearly identical to the older D3, it doesn't vibrate the sensor to shake dust away. But an integrated vertical grip makes portrait shooting more comfortable, and plenty of buttons let you change settings without having to dig into the menus. And if you're already familiar with pro Nikon bodies, you'll feel right at home with the D3X.
A dial to the left of the prism controls the drive mode, while three buttons above the dial let you control flash, bracketing, and shutter/aperture lock. Exposure compensation and mode buttons sit just behind the shutter button.
On the back, three buttons below the 3-inch 920,000-dot LCD give quick access to ISO, image quality settings, and white balance. These, along with switches for metering and AF modes, create a very efficient interface for photographers who need to change a setting at a moment's notice.
As usual with a pro DSLR, you won't find a pop-up flash. Of course, the D3X has a hot-shoe and is compatible with all of Nikon's current flashes, including the new SB-900 Speedlight ($400, street).
Two CompactFlash slots provide plenty of storage. Good thing, because with the D3X's huge RAW files, you'll need all the storage you can get. You can configure the dual slots as redundant backup, or one for RAW files and the other for JPEGs (handy in simultaneous capture), or so that the camera moves to the second slot once the first card is full.
And there's plenty of connectivity, too. Besides the usual composite video-out and Hi-Speed USB 2.0 terminals, there's a power input, a PC flash-sync terminal, and a 10-pin remote terminal, which lets you use Nikon's GP-1 ($210, street) GPS adapter to automatically add location and universal time code data to your images. Cool!