It's taken me about a month to settle on an auto focus strategy for my D700. I skipped several generations in film and digital SLRs, so getting up-to-speed with the D700 as well as re-learning some of the basics in focus and exposure has taken me a little longer than I'd thought it would.
Thanks to a couple of good forum posts - in particular this one - D700 and autofocus at Photo.net - I now have a much better understanding of how auto focus works in the D700, and in particular the focus points and what to expect in terms of different scenes, lighting and camera orientation. There's a consensus that the cross type focus points - 15 of them located in the centre of the 51 AF point matrix mean that you may occasionally find it hard to focus vertically (portrait) when using one of the edge focus points. In low light with little contrast and a lack of horizontal lines under the focus point this might be true - and I've been able to reproducibly see the difference in test shots against a target - but in practice - outside and focusing on people at events, or on the street, I'm finding the edge focus points are working ok.
So here's my recipe for fast(ish) focusing - in particular when photographing people at events or outdoors - in either landscape or portrait mode.
Remove the focus from the shutter button - (option a5:AF Activation - set to AF-ON button only). I was actually told to do this a while ago by a good friend, Patrick de Noirmont - but like most things - I have to learn them the hard way. :-) There are a couple of good reasons for this. For one, I was losing pictures when I was occasionally slipping, or releasing the focus after recomposing. The D700 is not a light camera (even without the battery pack) especially when there's a 70-200mm/2.8 lens attached to it and so it's possible to lose the 'feeling' of the half-pressed shutter button in all that weight. Moving focus off of the shutter button guarantees that you won't accidentally refocus after recomposing. What's more, you can always pull focus manually and know for sure that pressing the shutter button isn't going to change anything.
Leave the focus mode in continuous servo AF mode (the switch on the side). By moving the focus to AF-ON only - you effectively get both single servo and continuous servo focus. Press once for the equivalent of Single-servo mode - press and hold for continuous AF mode. Kills two birds with one stone and no need to flip the switch.
This one's important.. turn OFF the image review under the playback menu. Here's why. If you're shooting an active scene (again - an event or people moving around outside) then you're likely going to be moving the focus point using the multi-selector (multi-wheel), focusing, and recomposing repeatedly (especially if you're switching between horizontal and vertical composition). I want this process to be as fast and as fluid as possible. The bad news is that pressing the AF-ON button (or the AE-L/AF-L button) won't interrupt the image review like the shutter button does (turning off the monitor). If you have your eye to the view finder - having just taken a picture, and then try to move your focus point by pressing the multi-selector (before focusing again or recomposing) - you'll actually be moving through images in playback mode on the rear screen. If you don't turn off image review - then you'll have to press the shutter button first - and while that might not sound like a big deal, it's an extra button to push and when you want to move a focus point, refocus and shoot in under a second - it gets in the way.
And that's it... :-)
The results below - after a quick switch from portrait to horizontal - placing a focus point on the eyes (yes - the eyes) with no recomposing.
Device: Nikon D700 Lens: VR 70-200mm F/2.8G Focal Length: 180mm Focus Mode: AF-C AF-Area Mode: Dynamic, 9 points VR: ON Aperture: F/2.8 Shutter Speed: 1/125s Exposure Mode: Manual Exposure Comp.: +0.3EV ISO Sensitivity: Auto (ISO 1800)