mdougc Loc: Sarver, PA

I've stepped up to trying to use 2 Godox TT685C Thinklite slaves triggered by the Godox X1C. Question: If both lights are set for TTL radio wireless slave (and pointed at the subject from slightly different angles), and I use the camera FE Lock to meter on the subject, does the trigger "know" that 2 flashes are being used, so it reduces the power on each flash proportionately?
I experimented with this setup, and got bad overexposure every time. What do I not understand? Are there any (free) videos out there to show me the fundamentals of multi-light triggering?
Thank you.

lamiaceae Loc: San Luis Obispo County, CA

Hmmm. That might be why friends, teachers, and manufacturers told me to get two manual flash units and pass on the TTL. Just do a slight bit of math and shoot with manual flash.

CO

I've been reading the user's manual for your Godox X1C online. It looks like you can adjust groups A, B, and C individually or set all groups simultaneously. I can see how there's a chance of things going wrong in TTL mode. In TTL mode, the camera is measuring the reflected light and calculating the correct amount of flash needed. If both Godox TT685C Thinklite slaves receive that information, there would be over compensation. I don't think it can individually adjust the two slaves. What if one slave is close to your subject and one slave is far away? Almost all of the light falling on the subject is coming from the close slave and very little light falling on the subject is coming from the far away slave. The system cannot know that you have the slaves set up that way.

When using two slaves you should probably use the system in manual mode and use a light meter to measure the output from each slave individually.

I use a PocketWizard Mini-TT1 on my camera and put my Nikon speedlight on a PocketWizard Flex-TT5. Those units support TTL metering. I've done two light setups but that was with one studio strobe and one speedlight. I set the studio strobe output manually.

mdougc Loc: Sarver, PA

Thank you. Now I need to experiment.

speters Loc: Grangeville/Idaho

You put each speedlight on its own channel/group, then you can adjust every parameter, right from your camera! That way you can also set your ratios!