Strange issue with Cybersyncs and strobes

Was wondering if anyone had experienced this or know what may cause it. When shooting long exposures at night along with either my monolight or speedlights, my cybersyncs will fire more than once. I am using a 5D Mk II, not second curtain sync and if the exposure is say over 15 seconds, I'll get 2 flash fires - one when I click the shutter and another before the shutter closes.

Any ideas as to why it fires more than once?

Just curious - Are you using a set shutter speed or bulb mode?

You could put an ohm meter on the camera's hotshoe contacts to see if it keeps the circuit closed for the duration the shutter is open. If that's the case, then the cybersync transmitter apparently fires again when the shutter closes and the circuit opens. That's the only theory I have.

The next question would be, does the second flash fire when the second curtain begings to close, or after it's closed? Some testing would answer that question, and if the shutter is closed then it's nothing to sweat.

But if this behavior poses a problem then you might consider taking the transmitter off the hotshoe and firing the flash manually while the shutter is open.

Curtis N wrote in post #13107836
Just curious - Are you using a set shutter speed or bulb mode?

You could put an ohm meter on the camera's hotshoe contacts to see if it keeps the circuit closed for the duration the shutter is open. If that's the case, then the cybersync transmitter apparently fires again when the shutter closes and the circuit opens. That's the only theory I have.

The next question would be, does the second flash fire when the second curtain begings to close, or after it's closed? Some testing would answer that question, and if the shutter is closed then it's nothing to sweat.

But if this behavior poses a problem then you might consider taking the transmitter off the hotshoe and firing the flash manually while the shutter is open.

A transmitter battery that is near the end of its life span can cause Cybersyncs to fire randomly.

Thanks for the ideas - I'll do some troubleshooting and see what I come up with!

James

Oh - I am using a set shutter speed - the problem seems to happen at SS longer than 10 seconds.