> With D600 the AF detection limit of the central point is F8
You're misinterpreting the specification. That means that the system is not guaranteed to AF with a lens that is slower than f/8. (Or, more likely, a lens combination slower than f/8 - such as a f/5.6 superzoom with a 2x TC, which is net f/11.)
The reason for this is that AF (as well as metering and viewing) is done at full aperture, regardless of the selected shooting aperture. So for example, since I often shoot macro at f/11, f/16 or even f/32 - yes I know about diffraction - I'm still metering and AF at f/4 or f/2.8. There is no reason to switch to MF for those reasons. (However, for many macro subjects, MF is a better way to work since the placement of the AF target is often less precise.)
_____ Brian... a bicoastal Nikonian and Team Member
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