E-M10 & flashes
in a previous thread I was able to clarify, that certain Metz flashes do work as wireless slaves in TTL with the E-M10. I shall get a Metz flash as soon as Metz have successfully concluded their tests with the E-M10.
Meanwhile I am trying to improvise with a pair of old Oly FL-20 flashes left behind from a Camedia setup and some Vivitar 283 units with Vivitar SL-2 optical slave cells connected. My simple understanding is that an optical slave cell reacts to a burst of light like another flash and triggers its connected flash.
Setting up the FL-20 in the E-M10's hot shoe and the Viv 283 with its slave cell about 1 m apart, camera menu set to flash, I had the following happening:
FL-20 in TTL, Viv 283 in any of the auto positions of its measuring cell - no flash firing
FL-20 in Auto, Viv 283 in any of the auto positions of its measuring cell - no flash firing
FL-20 in TTL, Viv 283 in manual - FL-20 firing, Viv sometimes (however, difference in light output enormous, several stops)
FL-20 in manual, Viv 283 in manual - both flashes firing securely (however, difference in light output enormous, several stops)
FL-20 in manual, Viv 283 in manual with Varipower module set to 1/32 - both flashes firing securely (harmonious light output, needs fine tuning).
My question: what does the FL-20 and/or the camera E-M10 do in TTL mode that prevents the optical slave-connected Viv 283 from firing? Preflashes? Anything else?