With the EOS 7D, all 19 AF points are cross type, but the blurb states that:
"for enhanced precision, the central AF point features extra sensitivity when used with lenses having a maximum aperture of f2.8 or faster" (taken from Canon's official EOS 7D brochure)
Does this mean the centre AF point is double cross type or have an additional horizontal / vertical line activated at f2.8? Or is it just a more sensitive standard cross type sensor? I can't find anything in Canon's literature or in the likes of dp review that clarifies it.