I took it to a shoot the other day that was in a room with an electron microscope and I could not get it to sync with my other flash. It was embarrasing to have the poor girl sitting there with me not able to figure out what the problem was. I have it set to slave, and it is for sure going off, but it is either before or after the shutter closes/opens. I tried changing the shutter from rear to front sync and neither works. I can see the flash go off through my viewfinder, but it does not show up in the image. If I set it to 1/2 power it does fine, but 1/1 it just won't sync. What am I doing wrong?