<p>Mark, I find that with many other guests wanting a piece of the action at the first dance, on-camera flash serves me best. But I use rear synch with the flash, keeping this about 1/30 or 1/60 for the first dance (slower if it picks up a pace) but allowing this to fall to 1/8, 1/15 etc during the main dancing; the dragged shutter allows both the exaggeration of the many colours from disco lights and dj lighting, and also creates a movement in the dancers rather than static frozen-in-time characters which I hate when the pace of the dancing is hectic.</p>