Still no wiser on what the LC4 is, but the ST-E2 is not really an IR trigger. It sends pulse-coded strobe trigger and exposure data which are as readily accepted in visible light (as they are from a 580EX in Master mode) as they are in IR. The ST-E2 only has an IR filter so it does not contribute to the main exposure. In fact, if you remove the IR filter, you get more range (not recommended - just use a 580EX).