#9. AF sensor has 45 user-selectable AF points
The 1D Mark IV uses the same 45 AF point layout as Mark III, but the 1D IV’s new low-noise AF sensor has 45 user-selectable AF points. This is the same number of AF points available on the 1D II/N but significantly more than the 1D III’s 19. If you prefer the 1D III way, Custom Function C.Fn III-10 will let you configure the camera for 19 AF points – or 11, or 9 inner or 9 outer.