You're not just going for focus, though. You're going for a finished product with dynamic range -- it's easy to perfectly focus onto a dark black blob, but that

You're not just going for focus, though. You're going for a finished product with dynamic range -- it's easy to perfectly focus onto a dark black blob, but that doesn't make it recognizable as a human being. You might need to overexpose the rest of the frame, so that the skintone darks are bright enough to be interesting. That's doable, but it takes either a human touch or a digital camera with facial-recognition technology to figure out that's what's happening instead of just going for the bright zones. (And then you get a bright white blob if there's a white guy in the frame.)