Master and slave question

[agentm]

I recently got a new 580 EX flash. I also have a 550 EX.

I tried to play with the master and slave option to make both flashes go off.
What I discovered was that there is a small delay before the slave goes
off. Why is that? Aren't they suppose to go off at the exact same time.
When I swop the master to be the slave and vice versa....the same happens.

???

[iof]

Is this happening in actual use, or when you press the pilot button on the master? If the latter, everything is working fine. I have no idea why they have done things this way, except maybe to indicate you are in test mode.

[agentm]

AAAAAH.... I was pressing the pilot button.... I will put the flash on a body and test again

[DaveG]

AAAAAH.... I was pressing the pilot button.... I will put the flash on a body and test again

When you use the flash for real imaging you will still get two flash pops. That's the nature of E-TTL. When you use it with just one flash the first pop helps figure out the exposure. When you use it with wireless the first pop from the Master tells the Slave how to behave as well as providing exposure information.

Here are a few suggestions that might help in regards to the Canon wireless system: 1) Put the Slaved flash on Group B. The Master should be left alone and it will default to Group A. 2) To get a 3:1 lighting ratio you actually select 1:3 on the back of the flash. I know that this sounds weird, and every once in a while I figure out why this happens, but more importantly it DOES happen.

I'd suggest that you figure out a way to flag the slaved flash. I use self-adhesive Velcro, and I've stuck a piece of the soft side Velcro on the top and both sides of both of my 420 flash's. I then can put a piece of the hard Velcro onto some black cardboard cards. I always use the card on the side of the flash closest to the camera. This prevents flare. With the aid of these cards I've moved around to some extreme flash-to-subject angles, which flare wold have ruined. Often I will use a card on the other side of the flash as well to control where the flash is going, and to keep it off of things like projector screens.

I use a light stand to mount the slaved flashes. On the top is a very inexpensive "Umbrella Bracket" available at B&H for about $15. This bracket has a "non hot" hotshoe on top and it pivots to let me aim the flash head. And once in a blue moon I'll actually use it with an umbrella!

Canon Wireless is Line-of-Sight, and the Slave MUST "see" the pulse that comes out of the Master or it won't work. Turn the body of the Slave towards you and the Master position. The Slave will pulse a Bright red light and that will give you a good confirmation that it's pointed at you. You also keep that pulse off of the subject, which would otherwise be extremely distracting to the subject and the audience.

Now once in awhile in small room you could get some happy reflections off of white walls and you might get a way with a little less than Line-of-Sight. But I'd take LOS as a rule and be happily surprised when non LOS does work. I can assure you that in a big room it's LOS or nothing!