[Gidders]

Has anyone tried using this mode? Normally I use my speedlites in ETTL, or full manual mode & meter the output.

However I want to use my 580EX on my Panasonic GX7 wandering around at a at party where I wont be able to meter the flash & obviously I can't use ETTL. From what I've read, it suggests that this mode is similar to the thyristor mode of yesteryear where the flash output is measured by a sensor on the flash unit & cut off when sufficient light has been delivered.

It works... in that the flash fires & the exposure is consistent... but its consistently ~2 stops under exposed. Ok I can create a work around by setting the camera at f2.8 ISO 200 & the speedlite to f5.6 ISO 200 to fool the speedlite into delivering 2 stops more light, but I don't understand why I'm getting this behavior. Interestingly I get the same -2 stops using this mode on my Canon which suggests its a speedlite issue.

Anyone any ideas?