I may be answering my own question here but I figured I'd give it a shot. I have a 40D. I also have a 430 EX II. Now i was told that I cannot trigger my 430EX as a slave with another 430EX set as Master. I was also told, that if I were to get another 430EX II, I still wouldnt be able to set one as master and the other as slave. (Apparently the 60D can do this with its pop up flash). So essentially, does that mean I have to buy a 580EX II to act as my trigger for my 430EX? Could I just buy the ST-E2 (transmitter) and use THAT to trigger my 430EX? Or can I essentially do both???