My camcorder has several shutter speeds available, ranging from 1/400 down to 1/60 second. The default is 1/400 with shows about 80% of the screen as dark. When i set it for 1/60 the dark bands disappear completely.
Setting your shutter speed to 1/60 second will work for NTSC video systems because it is based on 30 frames per second (actually, it is 29.97 or something close to that).
On PAL systems, shutter speeds of 1/60 second may still cause dark bands because PAL is 25 frames per second.