Paul C. Buff, Inc. Technical Forum

I want to use 2 Einstein flash units for high speed photography. I plan to use the Action Mode at 1/8 power to obtain around 1/10000 flash duration.

Can I use one Einstein as an optical slave? Would the 2nd Einstein as optical slave be able to fully sync when they are in Action mode? Or do I need to run hard wire sync cables to both units?

As long as the slave eye can see the flash from the first light, it will sync instantaneously.

While the second unit will receive the optical signal instantly the is a short ionization time before it reaches full output . . . about 50usec. So, indeed, there will be two pulses of light 50usec apart that will sort of blend into one. That's 1/20,000 second. The effect will probably be to lengthen the effective t.1 time to about 1/7500.

You could eliminate this with a splitter to connect the camera hotshoe to both lights, or use CXSCV modules on the Einsteins and fire them from a CST.