Z innych źródeł, np.:

"The 20D and more recent cameras with Digic II processors use an exposure method designated as E-TTL II. Canon abandoned the use of the active AF in the flash calculation."

http://super.nova.org/DPR/Canon/TTL/

"The flash metering system is also no longer linked to the AF system, where in the old E-TTL metering bias is given to the selected AF point. Rather, E-TTL II compares the ambient and the pre-flash light levels of the scene to determine where the subject lies."

http://en.wikipedia.org/wiki/Canon_EOS_flash_system