I've downloaded and am reading the user manual while waiting for my 5D3 to arrive. The AF microadjustment described on p. 104-109 has new capability (to me) that allows for separate calibration at each focal length extreme of a zoom lens. The manual calls these settings W (wide) and T (telephoto). Once these settings are stored in the camera for a specific lens the adjustments for other focal lengths are automatically scaled by the camera based on the W and T settings.
I previously have attempted calibrating my EF-S 17-85 zoom with my 7D using the LensAlign MkII tool. The 7D allows for a single microadjustment - obviously a limiting choice for zoom lens. Seemed like a capability only for prime lenses.
The W and T settings may have been in 1D models for quite some time, or it could be new to the 5D3, and likely the 1D X too.
Does anyone have any experience with the W and T capability and can comment on its effectiveness?