ST-E2 fires 540EZ

I just realized that my ST-E2 will fire my 540EZ on a WEIN optical slave. Unfortunately, it's the focus assist or something since it's not in sync. I tried turning off the focus assist on my 5D (custom function 17) but to no avail. The downside here is that I have to hide my 540 from the ST-E2 which means moving my 550EX out front and putting the 540EZ behind the camera. Are there any other options?

No, it's not the focus assist that's triggering the optical slave. It's the command pulse emitted by the ST-E2 before the curtains open. You can defeat that by putting a piece of tape over the 4 dedicated pins in the hotshoe of the camera. They won't be required since you won't be able to use the 540EZ in ETTL mode, anyway.

Thanks PacAce. I'll give that a try right now.

Ok, tried it and have the same problem but in a better way. With tape covering the 4 pins on the 5d hotshoe, the ST-E2 will still fire the 540EZ but now it's in sync with the camera. Of course this is manual mode only.

Hinson wrote in post #4744212
Ok, tried it and have the same problem but in a better way. With tape covering the 4 pins on the 5d hotshoe, the ST-E2 will still fire the 540EZ but now it's in sync with the camera. Of course this is manual mode only.

Oops! Sorry, I missed the part about you also wanting to use your 550EX in the set up.

Let me rewind and start from the beginning. If you want to use the 550EX in ETTL mode controlled by the ST-E2, you will not be able to use the 540EZ in the mix using the Wein optical trigger because of the preflash emitted by the 550EX. You might be able to get away with it if you use the Wein "smart" optical trigger which supposedly can be made to ignore the preflash but I have no personal experience with any of the "smart" triggers.

I don't think "hiding" the 540EZ from the ST-E2 is going to help either because the 550EX also emits a preflash. Of course, you can hide the 540EZ from the 550EX, too, but then there would be no sense in having the 540EZ in the setup in the first place.

You can try the "tape" trick I mentioned earlier but then, the 550EX would need to be operated in manual mode, too.

Can always trigger the 540 by the old fashioned way: a hardwired sync cord.

PacAce wrote in post #4744416
Oops! Sorry, I missed the part about you also wanting to use your 550EX in the set up.

Let me rewind and start from the beginning. If you want to use the 550EX in ETTL mode controlled by the ST-E2, you will not be able to use the 540EZ in the mix using the Wein optical trigger because of the preflash emitted by the 550EX. You might be able to get away with it if you use the Wein "smart" optical trigger which supposedly can be made to ignore the preflash but I have no personal experience with any of the "smart" triggers.

I don't think "hiding" the 540EZ from the ST-E2 is going to help either because the 550EX also emits a preflash. Of course, you can hide the 540EZ from the 550EX, too, but then there would be no sense in having the 540EZ in the setup in the first place.

You can try the "tape" trick I mentioned earlier but then, the 550EX would need to be operated in manual mode, too.

Totally understand and both units are operating in manual mode. My question originally concerned the 540EZ firing out of sync and thereby rendering it inoperative for the exposure. I realized this when I moved it back to get more shadow and actually got more light. It was then that I started playing around and found that the ST-E2 was firing it, albeit out of sync.

Now, with the tape applied and the 550EX out of the equation, I can fire the 540EZ just as if I had radio slaves hooked up. I'm trying to figure out how this happens.

Hinson wrote in post #4744472
Totally understand and both units are operating in manual mode. My question originally concerned the 540EZ firing out of sync and thereby rendering it inoperative for the exposure. I realized this when I moved it back to get more shadow and actually got more light. It was then that I started playing around and found that the ST-E2 was firing it, albeit out of sync.

Now, with the tape applied and the 550EX out of the equation, I can fire the 540EZ just as if I had radio slaves hooked up. I'm trying to figure out how this happens.

There's nothing to figure out here. If you have all the dedicated pins taped up, the only pin making contact with the ST-E2 is the sync trigger pin which tells the ST-E2 to send out a "fire" command to the slaves. Actually, it doesn't really matter what is encoded in the command. All that matters to an optical slave is that it's a relatively bright light even though you can't see it since it's IR and it's emitted when the shutter curtains are open. So, the net result is that the optical slave triggers the slave in sync with the camera.

BTW, the sync trigger pin is "hot" only when the shutter curtains are open.

jmb4370 wrote in post #4744467
Can always trigger the 540 by the old fashioned way: a hardwired sync cord.

Good point, too.

Ah Ha! (as the light bulb goes on) I didn't realize that the IR burst was bright enough to trigger an optical slave. See, even us old coots have room to learn.

Thanks guys. This opens up a whole new world.

PacAce wrote in post #4744494
BTW, the sync trigger pin is "hot" only when the shutter curtains are open.

Thanks for that also. I did some quick tests and I can sync the 5D at 250 with those four pins taped.

Glad I could help, Hinson.