When taking a picture, tap the screen on the part of the image you want to focus on. This can either be a close-up item or something in the background. The iPhone will focus where you tap for a clearer picture or video.
The exposure can also be altered, or locked in place, when focusing. This ensures the shot is properly lit, or can create a cool-looking effect. While setting the focus you’ll notice a small sun icon next to the yellow box. Tap this and slide your finger up or down. This can help when taking shots in low-light conditions or in bright sunlight.
To lock the exposure, tap and hold a part of the image for a few seconds. You’ll now see the message AE/AF Lock across the top. You can now move the camera to another location while the exposure stays the same. To reset it, just tap the screen again.