Cheap radio trigger (1 transmitter, 1 receivers), 2 x 580exII, weird behavior

[tihophoto]

Hi all, first post here in the forum.

I've read all (I hope) posts related to firing multiple speedlites with a wireless trigger and I didn't seem to find an answer to my issue.

I'm shooting with a 40D and 2 580exII speedlites. During the time I had only 1 of them I bought a cheap radio trigger — some Phottix (~$50 probably). It worked very well when firing one of the flashes.

Then I bought another 580exII and I've set them up like this:
— The Phottix transmitter is on the 40D's hot shoe
— The receiver is on the 580exII's hotshoe mount. That speedlite is set as a master
— The 2nd speedlite is set as a slave. No radio receiver there.

Both Speedlites are in softboxes (60x60cm) similar to Lastolite's EazyBox.


The first tests I did were at sunset. It was very cloudy and almost dark. The photoshoot worked just fine and I was pleased with the results. I did a few tests at home. Again without any problem.

Then I went to shoot again at sunset, but there were no clouds at all, i.e. the sun was still shining. There the weird issues started popping up one after another:
1) When the master Speedlite is at zoom > 50mm, the slave won't fire. If I set the zoom to 50mm or less, the slave fires

2) When both are firing, but the sun is still shining the result image looks like there was no flash at all. This makes me think the Speedlites do not sync with the shutter.

3) If I move the master speedlite on the camera hot shoe, it works just fine no matter if there's sun or not

4) When the sun goes beyond the horizon (getting darker), the set up with the master flash off the camera (and using the cheap radio trigger) works just fine.


So, I think #1's reason is related to some sort of a "visibility" between the flashes (NOTE: the flashes are behind the softboxes, so they don't see each other directly)

But the biggest question is about #2. My suspicion is that under sunlight it takes more time for the Speedlites to negotiate the light emitting and they probably fire after the shutter gets closed. Tried with higher and lower (down to 1/80) shutter speeds, no success. I see the flashes are both firing, but the photo is still dark. When I stop the slave and set the 580exII to master = off — it works just fine. The image is properly exposed.


I think I should probably buy a pair of receivers for both Speedlites, but how am I sure I won't have the same problem with them?

One more question —*If I work with a pair of receivers, do I need to set the Speedlites to Master and Slave again?

[curtscamera]

Interesting that you got it to work this way at all. Daisy-chaining like the setup you described would not communicate any useful information to/from the Camera and the Master. The ONLY signal sent to the from your camera mounted radio trigger to the 580EX-II is the one that tells it to simply fire. Power levels etc. wold have to be set manualy on the flash. If the 580 is communicating with the 430EX-II from that point, I don't understand it. There is a thread going on in another section titiled: 580EX II as Slave and Master, that may shed some light on your situation.

[tihophoto]

curtscamera,

Thanks for the reply.

I not only made it to work under dark situations, but I also made a few hundred images like that and guess what the disappointment was when I went for the next 2 photoshoots under bright sun and it was simply not working

And yes —*I've been on manual mode both on the camera and on the 2 580ex II's.

It seems mixing the IR and radio communication is pretty unreliable (found it the hard way). So I better buy a set of radio triggers.

[curtscamera]

I'm going to have to check that out. I incorrectly identified your second flash as a 430ex-II. Sorry. I was reading the other post and mixed it up.

[tihophoto]

No problem.

My personal conclusion is that:

1. When the master flash is on the camera, it's negotiating the process with the slave properly and it synchronizes everything with the shutter. This means that during the negotiation the shutter may not even start to open. After the parameters are all set, the very exposure is initiated.

2. When the master flash is on a "trigger-only" radio receiver (while the Slave is communicating with the master by IR) there's a complex communication between the flashes and while the camera says to the trigger "Hey, I'm opening the shutter", the trigger tells the master flash —*"Hey, it's time to turn the lights on". At this time there's no communication back to the camera and the camera makes the exposure, while at this time the Master and Slave keep talking to each other. At the time the Master and the Slave finish their communication it's too late, because the shutter has been already closed. So even if I'm on Manual on both flashes, it seems like there's still some talk being made which is much longer than the shutter speed.

I'm probably wrong, but this conclusion sounds technically sound to me.

As I said, I would not try this set up anymore for any serious project, because it's unreliable. But I think it would be helpful for other flash freshmen to know the reason why it's not working like that.