The autofocus feature on the iPhone is pretty good, with its ability to pick out faces and adjust the white balance and exposure to focus on them. But as magical as this technology may seem, it's no substitute for human touch.
Let's say you're snapping a photo of a woman showing off her engagement ring. You'll want to focus on the subject's ring, not necessarily her face. Your phone's autofocus will dutifully draw a box around the fiance茅's face, and leave the ring relatively blurry. But, if you tap on the ring on your phone's screen, the focus will shift.
This works particularly well when shooting video. As you film, simply tap on whatever you want the camera to focus on.
