Frank Kimble , Jul 26, 2007; 10:25 p.m.
The flash will produce most of the light indoors. If you want the background dark then pick a fast shutter speed. If you want to pick up some of the ambient light in the background then pick a slow speed. I like to think of it as taking 2 separate pics at the same time, the aperture setting = flash setting are used to take the pic of the main subject. The shutter speed along with the already set aperture is used to take the pic of the background.