I'm really interested in getting an external flash to use on and off camera, but probably mostly on. But I'm a bit leery of the $250+ price tags of the ones specially made for use with m4/3, with TTL metering and all that. How would a non-m4/3 flash work with, say, my GH2? Would I have to set everything on the flash manually? Would I be in danger of having everything horribly overexposed if I tried using it as fill flash in the daytime?