The EOS R3 will benefit from the advanced AF systems introduced in the R6 and R5 cameras as well as employing deep learning technology to enhance the eye and body detection. Currently the Canon AF system has options for Eye and Head detect, but will be introducing a new Torso Detect function as well. (Presumably useful for any sports photographers who’s subjects wear helmets or masks of any sort.)
The camera also introduces a new system of Eye Control AF through the electronic viewfinder. Eye control AF was introduced in Canon Cameras way back in the early 90’s, but with the technological advancements in the intervening 30 odd years the EOS R3’s new Eye Control system promises to be more reliable while also incorporating more features overall. (Coincidentally the last camera to carry this Eye Control AF was the EOS 3, which was also the last EOS camera to carry the ‘3’ moniker until the EOS R3 as well.)
According to Canon, the EOS R3’s EVF will offer the ability to set “the initial area for AF tracking by simply looking directly at the viewfinder location where they (the photographer) want to begin AF.” The camera will then focus on and track subjects in that location of the frame automatically, as long as Eye Control AF2 and Servo AF are active.
It is unclear if the Eye Control AF will work continuously in video mode, but it will likely be useful to sports or wildlife photographers where milliseconds can be the difference between a great shot and missing the picture.