I have a problem that I just can't solve and I'm hoping someone here can help.
It happens at wedding receptions when I use a 580EX II on camera and trigger an Einstein (or Alien Bee) with Radio Popper Jr2's (also happened with with the original Jr's). The trigger is connected to the sync port in the camera and the 580 is in the hot shoe. For some reason, the only way I can use the external light is if the 580 is in manual mode.
I'm well aware of the pre-flash which can trigger the external light so I always make sure the optical slave is disabled on the external light. I've even fired the 580 by itself to confirm the external light is not triggered by it. Then, with the 580 on ETTL, I can see the external light flash but it is not in sync and does not show up in the exposure. For the life of me I cannot figure out why this is happening. I set my on-camera 580 to manual and boom, it works perfectly. I set it back to ETTL and no external light. I test fire the 580 and the external light does not fire.
So, I think there must be something in the camera (5D MkIII) that needs to be changed.
Has anyone else had this issue or can you shed some light on the problem?