Photos literally don't exist without light, and any photographer working outside needs to know precisely where the sun will be at any given point during the day. This app spits out that info instantly, locating and graphically mapping where the sun will be via an internal database of more than 30,000 locations around the world. Different modes include HelioMeter, which shows the sun on a compass dial; Virtual Sun View, showing an overlay of the sun's path on an image snapped by the camera; Map View, showing the sun on a map; and Sky View, which shows the sun's path across the sky. The app ain't cheap, but photographers, and cinematographers especially, will find it invaluable. [$29.99; iOS]