I did a photoshoot early Saturday morning and realized that eye autofocus has problems when people's eyes are not fully open. The light in Vegas is typically one of two types, too much and not enough. Early morning and late afternoon is the worst as the sun is on the horizon and often in the model's eyes, which causes squinting. If my R5 can't see enough of the eye, it refuses to lock on. It's not a major deal but I found it interesting that the camera couldn't see an eye if the model didn't have her eyelids mostly open. Logically, that's to be expected but it's something that I need to keep in mind when taking quick shots and don't have time to study the viewfinder before pressing the shutter button.