Brian and Abby share a walk along the promenade and spend a while watching the romantic sun set. Immediately afterwards, Abby says her goodbyes and walks away. Not only is Abby's face well lit from the side, but there are strong shadows from a fence cutting across the sidewalk.
When is taking photographs of Abby, he switches from a tripod-mounted to a camera to a hand held camera. When he does this, he doesn't change the flash to the new camera (the flash hot shoe is shown to have nothing connected), yet the flash still fires.
The flashes in question are studio flash heads powered from a remote pack. They are fired via a PC sync cord which can be clearly seen attached to the PC sync socket on the left hand side of each body.