Face Detection is a feature of the iPhone that adapts the focus & exposure automatically when a face is present in the shot. This feature is only active when taking a picture but this hack allows it to work actively when shooting video. This is really nice as the environment can change quickly during a video and typically you want the video focused on faces if they are part of the shot. This hack is available in Cydia for free.
FaceDetectionDuringVideo
May 8, 2013 by
The fact that focus and exposure can always be attained on the go while shooting a video, and with quick adaptation is really great. The iPhone camera technology is really fast advancing. There is this one I do with my iPhone…I can focus on image that is in front and set my exposure for what is behind (like background light). Wonderful innovations from iPhone.