I have a Nikon Coolpix 8700 and want an external flash that has the capability of being held away from the camera. Can any flash do that or do I need a special one with some kind of adapter cord? The Nikon brand is so expensive, so I currently looking at the Sigma EF - 500 DG Super TTL and the Sunpak PZ - 5000 AF TTL flashes. Are either of these compatible flashes? Do you have better suggestions?