I never had much luck triggering the YS-90 optically for TTL flash on some older Olympus cameras. The E-PL1 will be worse, because it has 2 pre-flashes close together prior to the main flash. The sensor in the YS-90 could not follow the flashes, and the strobe worked only in manual. It was actually quite usable that way though. It would trigger optically for the main flash, and you can adjust the power level on the flash as you prefer. I think you are probably stuck with manual on that flash, but it's got the 12 level settings.