I am gradually switching over from Canon DSLR gear to Sony mirrorless cameras and lenses. There are a lot of reasons why I am making this switch but, Eye Auto Focus has to be right at the top of those reasons.
I now own two Sony APSC mirrorless cameras, A6400 and A6500 (which I use as a two camera system in shooting stills - with different focal length lenses... These cameras are APSC (1.5x crop) format and are really small in comparison to my Canon DSLR cameras.
The Eye-AF of these cameras is just great, especially with the A6400, although the A6500 has some bells and whistles that I enjoy also.
Sony has brought out a firmware update for their full-frame A7iii, A7Riii and A9 cameras that includes, not only human Eye-AF but, animal Eye-AF. The firmware update for the A6400 that will include animal Eye-AF will be released mid 2019. Alas, there are no plans for introducing animal Eye-AF for the A6500. However, even though the A6400 doesn't "officially" have animal Eye-AF, it still recognizes the features of some of my dogs as "faces" and does a limited Eye-AF.
Eye-AF for animals is the best thing since sliced bread hen shooting dog portraits, especially for dogs that have eyes which are large and which contrast with the color of their coats like in the Maltese above. Even without animal Eye-AF, it is so much easier to shoot dog portraits with my Sony cameras than it ever was with my Canon DSLR cameras. I can select continuous auto focus (AFC) and place a focus point over the dog's eye and the camera will hang on to that eye even if the dog or camera moves.
Since there are focus points virtually all over the frame, I no longer have to focus and recompose. But, with Eye-AF, the camera will automatically spot the eye and focus on it. It is like magic!
As far as shooting people, Eye-AF is the best thing since sliced bread, especially when shooting with a long focal length, wide aperture lens like an 85mm f/1.4 or f/1.8.
This was shot using my A6500 with the Sony 85mm f/1.8 lens which is a great portrait combination; especially when shot wide open!
The difference between the Eye-AF with the A6500 and the A6400 is that to get Eye-AF on the A6500, I need to press an assigned button while on the A6400, Eye-AF is on consistently. No big problem with the A6500 since the 75mm f/1.8 lens has a button that I have assigned to Eye-AF..
Another neat thing about the Sony Mirrorless line is that it is very easy to convert just about any brand or type of lens to use on the Sony. I shot this portrait of my daughter using a sixty year old, German Meyer Optik Gorlitz Orestor 135mm f/2.8 lens on my A6500. This lens was adapted to the Sony using a Viltrox EF-EII 0.7x focal reducer which eliminates the crop factor when shooting with a crop format camera.
The Viltrox Focal Reducer retains auto focus with my Canon lenses which have AF capability. In fact, IMO, the Viltrox does a better auto focus job on my long focal length Canon lenses than does either the Megabones IV or the Sigma MC-11.
I have several other vintage lenses which I bought for a pittance on eBay and which have very unique renderings. This was shot with another "oldie but, goodie" 50mm German Meyer Gorlitz lens for which I paid about thirty dollars on eBay. The optical flaws of this lens render a very interesting Bokeh...
These vintage lenses are all manual focus but, is exceptionally easy to use manual focus lenses on the Sony mirrorless cameras because of "focus peaking" which lights up the areas in-focus in a selected color.
After shooting with Canon DSLR cameras "forever"; it has been quite a steep learning curve to begin with Sony but, the results such as this portrait of a friend, shot with with the A6500 and Sony 85mm f/1.8 wide open, make it worthwhile...
Yep! I "could" have shot this with a Canon DSLR and a Canon 85mm f/1.8 lens to get very similar results. However, the Eye-AF made shooting this series of portraits quicker and easier with the Sony gear.