Dal link del sito ufficiale:
“ Eye Control AF
For the first time in an EOS R series camera, you will now be able to set the focus point in the viewfinder, by simply looking at it — for incredibly fast changes in where the camera focuses, or to set the initial point from which the EOS R3's AF system will track moving subjects.1
1During still-image shooting only, through the electronic viewfinder. Eye Control AF may not be possible, depending upon individual characteristics or shooting conditions, and may not be possible for users wearing bifocal eyeglasses, certain types of sunglasses or mirror sunglasses, or certain hard contact lenses. „
"Still Image" significa "modalità fotocamera", cioè non in video.
Dai, almeno le basi...