Hey i have one of those optical slaves The one i have it looks exactly like that one, is not the brand or the price but is the same one. Now, there is some sync problem with mine, When i fire it it fires 99% of the times BUT the flash will not sync with the camera... It happens some times even indoors, without any light and as closed or far as it can gets, i can see the flash firing but is not on the picture. I've tried all shutter speeds, but i don't think is a matter of speed cuz it does it sometimes only, and no matter the speed. Is this normal?