Warning -- Don't use Old External Flash Units

WARNING! 

Don't attach any old external flash unit to your digital camera before you read this POST! You may end up frying your camera!

DON'T DO: Don't attach any old external flash unit to your digital camera unless you know it's safe to do so.
WHY: Older flash units can have higher trigger voltages. What this means is that when they are triggered by your camera, they can produce a lot of voltage at its trigger contacts, which can end up going back into your digital camera and end up frying it, turning it into an expensive paper weight.

Now, with that said, there are some older flash units that are ok to use. So, if you have an older flash unit and you want to determine whether its ok to use with your camera, there is this site . . . (http://www.botzilla.com/photo/strobeVolts.html) [NOTE: I've listed this site on my Links page here for easy reference.] , but as the site even says itself "Follow at your own risk."

You can also measure the trigger voltage yourself, which is described at the above mentioned site as well, which is a little safer.

But, really, the safest is to refrain from using older flash units and get a modern external flash unit, which will end up having more cool bells and whistles and communicate with your camera for TTL exposure control a lot better anyway!

NOTE: There are ways to trigger these older flash units off-camera, without them being directly hooked-up to your camera. But if you, or someone, ever forgets that the old flash unit can blow-up your camera and puts it on your camera, then you're back to square one. For me, I've justed stashed away all my old flash units and gotten newer ones to be safe.

Take care & Happy Shooting!
Glen - DigicamJunkie.com