Hi all,
I have been trying to use my 550 EX as a slave unit being activated by the on-camera flash of the Canon 20D. I can do this with my Sigma flash unit as a "dumb" slave ie: it just fires with the output set manually, not TTL. I can use the Sigma as a TTL slave using the 550 EX as a master, but when I want to save weight and bring just one flash, I haven't been able to work out how to set off the 550 EX (channel 1, 2, 3 or 4, or as a "dumb" slave on channel 0).
Is this possible, or should I just bring the Sigma?
Cheers,
Andrew