Master slave flash anomaly?

[Valvebounce]

Hi Folks.
Another question about the Canon optical master slave flash gear.
My camera buddies and I were taking some macro shots of flowers last night, we started with my 5D with mirror lockup with a 550EX in master setting triggering my Triopo flashes on Slave Canon setting, all worked ok, pre flash as the shutter went up then main flash on shutter actuation. Result, well exposed shots.
Next photographer up was using a 7D with my 550EX, preflash on mirror lockup, solitary flash from 550EX, result underexposed shots. We also tried using the built in master, same result.
The third photographer, another 5D was using a 580EXII as master, this worked ok with mirror lockup as well.
I tried with my 7D and 7DII, same thing, no flash on slaves when shutter opened.
It all works when mirror lockup is taken out of the equation, it also all works on 5D and 40D with mirror lockup enabled, but the newer cameras only work without mirror lockup.
Any ideas, this has me baffled, I have no idea why the 550EX would trigger the slaves on an old camera and not on a newer camera only if shutter lockup is active. What has Canon changed?

Cheers, Graham.

 

[Valvebounce]

Hi Folks.
Ok I think I have got to the bottom of this, I believe that the issue is the preflash.
I think that the older camera bodies are initiating a metering preflash when the mirror locks up, and then another preflash (of no use as the metering sensor is covered by the mirror) followed by the main flash when the shutter opens hence the Triopo slaves fire correctly.
I think that the newer camera bodies are firing the metering preflash when the mirror is locked up, and then only the main flash when the shutter opens, hence the Triopo not firing the main flash as I guess it is not understanding this behaviour.
I tried the 7D's, I and II with onboard flash as the master and my 550EX as the slave, this worked perfectly, meaning that the old 550EX is made to understand the system on the newer bodies, I guess Canon knew where they were going.
Just to confirm my suspicion I tried setting a Triopo flash to the two non dedicated slave settings, one of which ignores preflash for working with an ETTL flash, the other setting is for manual flash.
When set to the ignore preflash setting it didn't fire, suggesting that there was only one flash, the main flash, when set to the setting for manual flash triggering, it fired, which I believe confirms my theory.
I know this is a "well what do you expect from cheap Chinese copies" situation, but frankly for about £50 I'm surprised they work as well as they do! And for £50 I can afford to use them in my mechanics shop for documentary type shots where I would hesitate to take expensive OEM flashes lest they get damaged.
Hopefully anyone who is interested in what I have tried to describe can understand my rambling explanation and methodology.

Cheers, Graham.

 

[MixPix]

"I know this is a "well what do you expect from cheap Chinese copies" situation, but frankly for about £50 I'm surprised they work as well as they do! And for £50 I can afford to use them in my mechanics shop for documentary type shots where I would hesitate to take expensive OEM flashes lest they get damaged. "

Agreed!