Given the number of messages here about focusing on one eye or the other, folks must like really shallow depth of field and don't seek to get the whole face in focus.I have a general question for the portrait photogs... How can you get an entire face in focus at f1.2? When I shoot my 50mm at 1.8 on an 80D, it's basically a crapshoot if I get a subject's face entirely in focus, and I can't really tell until I'm watching on a monitor. Any tips?
For fairly normal looking perspective in a head-and-shoulders shot, you want the subject 10 or so feet from the lens, for typical faces; maybe a little closer for folks with flat faces and a little farther away for people with bulbous noses. That is why many photographers prefer 85mm to 100mm lenses for such full-frame portraits: it puts the subject in the ballpark of that distance. 85mm at f/1.2 will give you about five inches of depth of field on a subject 12 feet away. So you ought to get the ears and nose reasonably sharp with careful focus, though not right on the eyes. Put the subject a little farther away or stop down a little, and the whole face should be in focus more easily.
Your 50mm f/1.8 on an 80D will put you about the right subject distance or a bit closer. So at 10 feet and f/1.8, you should have about 9 inches to play with.