Sadly, I have yet to find the "perfect" solution for off camera flash using speed lights. I've been through RadioPoppers (an early adopter), thru PocketWizard TT5 (also an early adopter) and am now using the Canon 600EX RT and transmitter. Each of t...
I forgot to mention one more thing. If one of my flashes is being used as a back light, hair light, accent light, etc, then eTTL doesn't really work for that scenario anyway. And so it's important to put that flash into manual mode. This gives corr...
Recently Canon came out with an upgraded firmware for the 5D Mark III that is supposed to help with the AF Assist. I'm not sure what the firmware does, and I haven't given it a try under similar lighting conditions (yet), but we'll soon find out if ...
I believe I have run into what you are describing and found "my" work around to the issue. At the time that I ran into this I had 3 off camera flashes going (none on camera, using Canon's remote to fire the flashes). And all three flashes were set t...