Questions about ETTL wireless master/slave setup

I've played with ETTL master/slave setup a bit, and found the following things. I just want to confirm my findings are correct.

1) when I set master to not-firing, it still fires, in both the preflash and actually shot. I set things to exposure to manual, took a shot with flash completely turn off, and with master turned on (slave turned off) and set to not fire, the exposure is different. the one with flash turned off is pitch black, the one with master "nont-firing" is underexposed about 1.5 stop

2) if I set ratio to 1:4, and FEC on camera to 0. that means the master will expose the foreground properly, and slave will be four times as powerful, and will therefore overexpose? I can't seem to get consistent result in this test.

3) Is there a way to make use of the external flashes focus assist beam without letting it flash at all?

I went for the STE-2 because I didn't want to waste a 580EX on top my camera when it could be used off to one side.

dr_who wrote in post #4505606
I've played with ETTL master/slave setup a bit, and found the following things. I just want to confirm my findings are correct.

1) when I set master to not-firing, it still fires, in both the preflash and actually shot. I set things to exposure to manual, took a shot with flash completely turn off, and with master turned on (slave turned off) and set to not fire, the exposure is different. the one with flash turned off is pitch black, the one with master "nont-firing" is underexposed about 1.5 stop

2) if I set ratio to 1:4, and FEC on camera to 0. that means the master will expose the foreground properly, and slave will be four times as powerful, and will therefore overexpose? I can't seem to get consistent result in this test.

3) Is there a way to make use of the external flashes focus assist beam without letting it flash at all?

1) When you set the flash to Master mode, even though its flash is set not to fire, the flash will still contribute a little bit of lighting to the shot, as you already discovered. That lighting is actually the command flash that the master sends to the slaves to fire. That command signal is sent when the shutter is open.

2) I'm assuming that one of the flashes, either the slave or the master, is the Sigma EF500 DG Super. What's the other flash? If it's a Canon flash, it's a known problem that ratios don't work too well with a Sigma Super in the mix.

3) I know it can be done with the EOS xxD series cameras but I don't think that feature is availabe on the 350D/XT.

PacAce wrote in post #4506623
2) I'm assuming that one of the flashes, either the slave or the master, is the Sigma EF500 DG Super. What's the other flash? If it's a Canon flash, it's a known problem that ratios don't work too well with a Sigma Super in the mix.

Thanks again Pac, the crowd here has always been very helpful. I have 2 sigma flash and a borrowed 580EX 2. I am extremely unhappy with the sigma now. Using 1 sigma as master, the other as slave, no ratio set. The FEC work only 20% of the time and most of the times I get random flash exposure. Yes, the sensor is aimed at the master. Using the Canon as master and master is firing, FEC works properly 80% of the time; setting master not to fire however, the flash always over expose about 1.5 stop (set to -2 FEC to get a proper flash exposure). Is this a known problem? Or is there something I did wrong? With this kind of reliablily, I'd say flashes are as good as junk.

Phew. I'm glad I didn't go for the Sigmas!

Actually, I nearly went for Sunpaks!

rhys wrote in post #4506718
Phew. I'm glad I didn't go for the Sigmas!

Actually, I nearly went for Sunpaks!

They work OK as the only flash. Wireless? forget it.

dr_who wrote in post #4506710
Thanks again Pac, the crowd here has always been very helpful. I have 2 sigma flash and a borrowed 580EX 2. I am extremely unhappy with the sigma now. Using 1 sigma as master, the other as slave, no ratio set. The FEC work only 20% of the time and most of the times I get random flash exposure. Yes, the sensor is aimed at the master. Using the Canon as master and master is firing, FEC works properly 80% of the time; setting master not to fire however, the flash always over expose about 1.5 stop (set to -2 FEC to get a proper flash exposure). Is this a known problem? Or is there something I did wrong? With this kind of reliablily, I'd say flashes are as good as junk.

What you are experiencing was the same thing I experienced when I had my EF500 DG Super. I called Sigma tech support but they couldn't help me because I was mixing the Sigma flash with Canon flashes and they couldn't guarantee compatibility with the Canon flashes.

dr_who wrote in post #4506729
They work OK as the only flash. Wireless? forget it.

Sunpaks would be great if combined with decent radio interfacing for a portable studio.

rhys wrote in post #4507315
Sunpaks would be great if combined with decent radio interfacing for a portable studio.

Rhys, how do you get dis-membered?

dr_who wrote in post #4508098
Rhys, how do you get dis-membered?

I got sliced-up by a Terminator reference