With a 400 5.6L are any of the AF points "cross-type" sensors? I have read the manual, and it seems ambiguous about this matter. With a 1.4 extender, only the center point AF is active, and it is not "cross-type." Please advise.
1D series cameras can AF to f/8 with the center point. This is why the 400 5.6L/1.4x combo only works at the center. Other Canon's AF to f/5.6 at the center.
He was wondering whether the AF points remain cross type at 5.6. As far as I know they only are with f/2.8 or faster glass. That said, my 1Ds II is blisteringly fast with the 400/5.6 without a teleconverter.
"All AF points are sensitive to horizontal detail, however for a lens with a maximum aperture of F2.8 or faster lens a vertical row of 7 points (as indicated in red in the diagram above, right) become sensitive to both horizontal and vertical detail, and the manual notes, are three times more sensitive than the normal horizontal sensors. Some other L lenses with maximum apertures of F4 or brighter make use of the center cross-type AF point."
