Slave flashes totally confuse me. Help?

[shyguyjay]

Hey all:

I've been confused about this for the longest time and can't seem to find any clear answers. I'm a newbie at wireless flash so please forgive my ignorance.

So I've recently ordered the 580ex II. Apparently it can act as a master. I also have a 480ex. This flash apparently can work as a slave. So obviously the 580 has to be on the hotshoe on the camera but how does it communicate with the 480? Do I need any additional wires or cables? And what about adding a third wireless flash or using the 580ex as a wireless?

All of this said, what then is the point of the ST-E2? If you can get a flash to act as a master, under what circumstance would you need the ST-E2 transmitter? And why do I sometimes see third-party manufacturers (like Alien Bees) selling multiple transmitters? Does every wireless (slave) flash you use need it's own transmitter?

I guess what I'm trying to figure out is - how can I go about using 2 flashes (one for a key or fill light and one for a backlight) and have them both be wireless.

Sorry, I know there are lots of threads on this but nothing that clearly gives me the answers I'm looking for. Thanks to anyone who can shed some light (no pun intended) on this situation.

J.

[Titus213]

I might be able to help you on some of this. The Canon ETTL system is a dedicated proprietary system and Canon seems to hold its design very closely. The beauty of the system is that it allows for automation with the camera including flash ratios while using multiple flash units that do not have to be directly connected to the camera. The ST-E2 basically lightens the load on the camera and allows all the flash units to be off-camera.

As to the systems used by others - generally they require the flash unit to be used in a manual mode and you have to manually set your power needs on the flash.

I am not familiar with the 480ex flash but assuming it is ETTL capable the 580EX will act as a master and allow the 480 to be controlled remotely. You can set ratios, FEC, etc from the camera using the system but the 580 will have to be connected to the camera.

[vetkrazy]

Like the man said one day "It's not rocket science" but it can be a challenge. First let me assume you are talking about a Canon 430EX. This is a slave only flash, you will need a 550EX, 580EX or ST E2 to fire it remotely. If you use the 550/580 it will need to be connected to the hot shoe, either directly or with an off camera cord. The use of the ST E2 allows for the use of many slaves in remote. The advantage is that they can be in groups and the groups can be fired with different ratios, some key, some fill. The 580 has the same ability but has to be tethered to the camera. I use the ST E2 with three strobes: key,fill, and backlight.
You asked how they communicate. It is IR and inside it works very well. In most cased it will bounce off the walls and trigger my backlight hidden behind some furniture. Out in the bright sun light it is pretty hit and miss unless you are close. Don't confuse Canon's wireless with anyones else's. It is proprietary and will not work with any others.

[Curtis N]

The confusion is caused by Canon's use of old generic terminology to describe something completely different from the original definition.

In the old days, a "slave" was simply a flash attached to a sensor that could "see" another flash and trigger the slave more-or-less simultaneously. With these setups, any flash connected to the camera could be a "master" and any flash connected to one of these sensors could be a "slave". Today, most studio strobes and a few battery flash units have slave sensors built-in for convenience. Output from each flash was either adjusted manually, or adjusted on each unit via their own automatic settings.

With digital cameras, along came Canon's proprietary E-TTL system (other manufacturers have similar systems). These systems use a pre-flash that fires before the shutter opens, and the camera measures light from this pre-flash to calculate the amount of flash required. Flash units designed for these systems have no internal ability to measure light and regulate their own output. This pre-flash would confuse old-fashined slave sensors and cause them to trigger prematurely.

So manufacturers developed highly sophisticated technology to use multiple flash units. The "master" flash now must be designed to communicate with the slaves, and the "slaves" now must be designed to accept instructions from the master and act accordingly. Old terminology being used to describe new and different technology.

Canon units with E-TTL slave capability are the 420EX, 430EX, 550EX and 580EX.
Units with E-TTL master capability are the 550EX, 580EX and ST-E2. The ST-E2 is simply a communication device with no flash of its own. As far as I can tell, the only advantage to the ST-E2 is that it's cheaper, smaller and lighter than the master flash units.

[shyguyjay]

Hey guys:

Thanks for all the thorough answers. This clears up a lot of the confusion for me. I took the plunge and ordered the new 580ex II so now I might have to buy a few more toys to complement it.

I always appreciate the friendliness and willingness to help on these forums.

J.