Autofocus
Like the D700, the D800 uses the Multi-CAM3500FX AF sensor, with a 51-point AF system. However, it is the same refined version as that found in the D4.
Refinements include 15 cross-type points in the centre of the frame compatible with lenses at f/5.6 or faster, and an 11 AF-point set-up that, when selected, is compatible with lenses at f/8, bringing the best of the focusing system to a wider range of optics. Furthermore, improved low-light performance enables operation at -2EV (for use under moonlight).
Although contrast-detection AF is claimed to be more precise than phase-detection AF (which is the type used in the D800 for stills), the camera was capable of producing sharp images. Once I was familiar with the AF system and after selecting the right mode for a scene, the camera is spot-on in virtually every situation.
Certainly in low light, it can pick up subjects and focus with minimal effect on speed. Impressively, even shaded objects in moonlight are picked up with minimal hunting. Most other systems simply would not operate under these conditions.
There are a few AF mode options, all of which can be seen and viewed through the viewfinder. Handily, the AF switch has been redesigned to include a button so the user’s eye can remain fixed to the viewfinder to navigate through the different modes.
AF modes include 3D colour tracking, single point, nine-point tracking, auto area, 51-point tracking and 21-point tracking. If there were time to compose the scene, I most often opted for single-point AF because this point can be selected from any of the 51 points in the central area of the frame.
