Originally posted by Winder I was shooting at F/2 or F/2.8 though and only the center 3 sensors are F/2.8 sensors. Most people however will be shooting at F/5.6 and could use the zone AF system
Only center points have f/2.8 baseline, but it does not mean, that the rest of them can't be used with that aperture. It just means they have narrower baseline and slightly less precision. BTW, judging from some marketing materials, only the horizontal pair of sensors have a wider f/2.8 baseline, vertical pair uses narrower f/5.6 baseline only, so basically those "points" work on f/5.6 precision and use an additional f/2.8 pair of sensors as a support when the system needs more precision with faster lens. I even doubt if they are used in the AF-C mode where the AF system is tuned for speed rather than accuracy.