I haven't noticed that behavior using a 600 as master.
July 28, 2014, 10:38:10 AM
Topic: 600EX RT & ST E3 RT - issues and testing (Read 3553 times)
I used to use 580 EX II as a master to trigger slaves as well, and I turn the 580EX II master flash to off. It will still pre-flash. It shouldn't contribute to exposure, as I've never noticed as issues in the end result.I tested this last week when someone else had posted it - I pointed my two 580EXII's at a mirror, one on camera and one off camera. I changed between the master being on and off and in both cases there was a hot spot in the frame - the only difference being when off the hotspot was slightly smaller. I tried it with both a 40D and 5D3. Someone else chimed in to say their 5D2 and 5Dc behave the same way.