During my wedding receptions I like to set up 1-3 flashes in manual power mode around the room. I'd also like to have a flash in TTL mode "on camera" set to -2 or -3 exposure compensation for some front fill.
I use the YN622CT transmitter on my camera and YN685s off camera. I use a Canon 600EXRT on a bracket with a YN622 receiver so it can be triggered.
The problem I've found is that while the TTL works sometimes, most of the time the TTL is way off, more so than if the flash were connected directly to the hotshoe. The problem seems intermittent and hard to replicate consistently. My old 580ex would do a full dump every shot on this set up.
Is there something I should be setting on the trigger or the 600EXRT? The only thing I can think of is that the manual flashes are firing too early and messing with the TTL preflash but I don't know how to make the manual flashes fire after the pre flash.
At this rate I'm thinking I need to find a trigger system that can be triggered from the PC sync port of the camera so I can keep the 600EXRT on the hotshoe. The YN622 can do this with a PC to hotshoe adapter but you then can't set the power on the remote flashes and they just dump full power.