03-13-2014, 11:20 PM
Hi Haring, SB-800 and SB-900 have built in radio to control other flashes. I am not sure up to how many. In addition you can control the intensity of each external flash through sb 800 or sb 900. I have SB-600, it doesn't have the same abilities. SB 600 can be used as off camera flash(es), it will communicate well with SB 800. And last, but not least SB 600 is un-expensive.