Olympus cameras (E-M1 in my case) are able to optically control Olympus flashes and adjust power accordingly, but are there third-party flashes that the Olympus can control? Many flashes can be triggered optically, but I'd also like to be able to adjust power of the slave flashes from the camera/flash combo.
Note 1 - this is a modification to the question found here, except I don't mind using the included flash to control the slaves.
Note 2 - Per the manual, Olympus lists 2 of their flashes as compatible (FL-300R and FL-600R), but the E-M5 could control the FL-36R and FL-50R, so there are flashes already missing from this list.