Like most recent DSLRs the D3x features live monitor view. It has two modes, one for hand-held shooting and the other for tripod-mounted studio work. In hand-held mode the camera uses the main phase detection autofocus system, which is much faster and more accurate, but does require that the reflex mirror flips down while focusing, shutting off the live view for a moment. The tripod mode is uninterrupted, but uses a single centre-zone contrast-detection autofocus sensor, which is painfully slow to operate.
While there's no question that live view does have its uses, the only implementation of it that I've seen that doesn't seem like a bolted-on retrofit is Sony's integrated dual sensor system, which allows uninterrupted live view with full phase-detection AF. Neither of the modes employed in the D3x are completely satisfactory by comparison; both are slow, and one completely wastes the camera's fantastic autofocus system. Although I've been using the camera for a couple of weeks, I've found that I barely used the live view modes at all.
Shooting in viewfinder mode the Multi-CAM 3500FX autofocus system is simply brilliant. It's the same system used in the superb Nikon D300, with 51 focusing sensors including 15 cross-type sensors that are faster, more accurate and more sensitive to light. It's unquestionably one of the best AF systems currently available, and works quickly and accurately even in very low light levels, although below a certain light level it requires an attached Speedlight flashgun to provide an AF assist light, since the D3x has no built-in flash.
The light metering system is equally sophisticated, using a 1005-pixel RGB exposure sensor and Nikon's 3D Colour Matrix Metering II system. It is extremely effective, coping well with difficult lighting situations such as strong backlighting or isolated spot-lit subjects. When manual bias is required the D3x offers exposure compensation of plus of minus 5EV in 1/3EV, ½EV or 1EV increments. Naturally centre weighted and spot metering are also available.
For very high contrast situations the D3x has Nikon's Active D-Lighting system, an automatic tone compensation system that enhances shadow detail while attempting to prevent burned-out highlights. It is a very effective system, with four manual levels plus an auto mode which seems to operate reliably enough to be left switched on as default. I could detect no negative impact on image quality even in very high contrast lighting.