Hi all- I'm fairly new to off camera flash. I usually just bring my cheap little 420EX along and bounce it around when I need extra light. However, I am interested in purchasing the 580EX (original or II, haven't decided yet) so that I am able to move the 420EX off camera. Since the 580EX works as the master unit, do I still need any type of transmitter/receiver system, or will the manual with the 580EX tell me how to work the two flashes together? I currently have a Vivitar 285HV that I use off camera with a cheap-o transmitter/receiver system that I got on ebay for like $30. I don't like it, which is why I am interested in working with the Canon Speedlites instead.