I have found that the STE-2 has some differences in use compared to using the 580EX as the master. The biggest annoyance I have is that I can't see how to set the 580EX on the camera to manual and still trigger the second flash on ETTL. What I am trying to do is create the smallest amount of fill flash possible (say 1/64 or 1/128 power), but having the ETTL do its job with a 2nd flash set to bounce off the ceiling. The Canon body and/or flashes only let me go to -3 EV on ETTL, which I find isn't enough when the subject is close to the camera, especially if the bounced flash is far away.
I CAN set the bounced flash to manual and achieve what I want, but it doesn't automatically adjust for distance as I move around a room...
[I did have a question in here about using the flash ratio with the 580EX on the camera, and thought I might be missing something. Turned out I was, the ratio does work with the 580 on the camera as group A, in Canon terminology]
3 hours ago