Help to set 550EX Master OFF

I am trying to set the Canon Speedlite 550EX Master OFF so that I can only trigger the 420EX as slave without firing the 550EX master on the camera. I follow the instructions of page 57 in the manual but there is something wrong for I cannot prevent the master flash from firing. What am I doing wrong?

I have the 580EX and it says to press zoom until the display blinks, then turn the dial until it says "off". Maybe your 550EX is similiar (except not via a wheel).


PS: It says it'll still fire a preflash because that's how it signals to fire the slaves. You may have it right already and are just seeing that preflash.

If you are sure you followed the instructions in page 57, then you are fine. You can verify this by taking a picture and seeing that the subject is only lit by the slave flash and not the 550EX mounted on the camera.

Even if you have the master flash turned off, it will still fire what looks like a preflash and that is normal. That is how it communicates with the slave. The main flash will be off when the shutter opens up to take a picture.

Thanks for that. In fact, it would be very helpful to have this clarification in the Canon manual.

In my manual it says it as a very clear footnote.

Yes, it's the same with the 550EX manual, too. There's a footnote at the bottom of the page.

But the note does not say that the flash fires a pre-flash, but a wireless signal to activate the slaves. At least in my manual it does not specify that there is a pre-flash.

With ETTL there's always a preflash. I haven't read the 550EX manual recently, it might be mentioned somewhere, it's not a bad manual but it doesn't cover absolutely everything.