This is a new one. I have a 580 and a 580ex2. I've used them both as on camera flash, often in master mode. All of a sudden, neither of them will work as master. When Master/Slave is turned off, everything is fine. With both, when I put them in Master they put out a tiny pop(less then the normal pre-flash), and will not trigger slave flashes, or provide exposure on the subject.
I find it hard to believe they both failed in the exact same way within days of each other. I've tried resetting my camera, and turning all custom flash functions off, still nothing.
To reiterate, I've used both flashes as master before, dozens if not hundreds of times.
An update: Same problem, with both flashes, on my 40D. In master, there is a tiny puff of a flash, but if won't trigger a slave, and doesn't record on the sensor.
Is it possible that I have the exact same fairly obscure problem with two flashes at the exact same time? Doesn't seem likely.
Also, same thing in manual flash. master/slave off, 1/4 power works like normal, but in master 1/4 power only puts out that little puff of flash, both cameras, both flashes.
Unless there is a coincidental failure in two flashes or two camera bodies, it seems there's most likely some kind of problem in one of the flashes that somehow affects their communication regardless of which is master and which is slave. At least that's the only way I see that a single fault could affect all the combinations you've tried.
Can you get hold of a third flash and try it with yours one by one?
