I have an 550 EX and I like to use it as a additional flash for my digital camera using the generic slave unit sensor. Is it OK ? Since I read some where from internet that 550 EX may damage if combined with generic slave unit. Thanks

-- Anna (sg@hotmail.com), December 02, 2000

Answers

I wonder if you're confusing the trigger voltage of a non Canon flash like a Viv 285 on an EOS body. That will do damage. The EOS bodies cannot handle more than 6 volts of voltage through the hot shoe or the PC terminal. All EZ and EX series units are below the 6v limit. The problems I've heard of with newer EX series flashes and wireless sync is that they will fire once and then lock up. With any kind of sync, RF or line of sight. I can't recall if people who have this problem just turn off the flash and turn it back on when this happens. If your digital camera has a hot shoe you could purchase an ST-E2 transmitter and that will send a signal to the 550EX and trigger it. That's all I have for you.

-- Colin Miller (ckmiller@pond.net), December 03, 2000.

Colin's right. There is no danger in using a generic slave attached to your 550EX, or any other Canon Speedlite, but it may not work. If it locks up after firing once you can manually fire the Speedlite and that should free it up for another shot.

The problem with this idea is that the 550EX will have no exposure control except manual, and will completely dominate yout on camera flash unless you select a lower manual power output. Normally that would be troublesome since you can't see what you're doing until the film gets back from the lab. Obviously that's not quite the same difficulty with digital cameras. '

The better way to do this is to use a Ikelite Lite-Link TTL slave for the 550EX. It will work just fine with your Speedlite and the on camera flash will control the exposure of the slave mounted light. So for $100 you can have wireless TTL metering for your digicam or any other camera you want to use it with.

-- Jim Strutz (jimstrutz@juno.com), December 03, 2000.