Jak tak procitam http://www.usa.canon.com/dlc/control...rticleTypeID=5, nemohu se nezasmat nasledujicimu vyroku:

Release/Tracking Priority (C.Fn III-3-3) was absent on the previous generation Mark III, but has been brought back as an important feature of the EOS-1D Mark IV.
This new setting, which was the only option for AI Servo AF release/tracking priority with the original EOS-1D, EOS-1D Mark II and EOS-1D Mark II N, was conspicuously absent on the EOS-1D Mark III. Now, EOS-1D Mark IV users will have the best of both worlds together with the new improvements to AF hardware and software.
Zkratka marketing funguje na 100%, odstranime funkci a v dalsi verzi ji s velkou slavou privedeme zpet. Mam pocit, ze tento model mark IV ma byt omluvou uzivatelum za nekym oznacovany nedodelek mark III. Ale je zase dobre, ze Canon nasloucha.