New flash, slave questions

[LeSueur24]

I just got a Canon 430EX (yay christmas!) and it works perfectly when it's on camera (Canon EOS Rebel) but do I need to have another speedlite to do the slave function? I noticed that a friend of mine just needed the built in flash on his camera to trigger his Nikon speedlite (he owns a D80), but when I try to use the built in flash on my Rebel the 430ex doesn't fire. Does the Rebel not support the slave function?

EDIT: And if it doesn't, are there any other wireless transmitters I can get that aren't as expensive at the Canon one?

 

[Tiberius47]

The built in flash of Canon dSLRs isn't compatible with the wireless flash slave system built into the EX series flashes, unfortunately.

You can get an optical slave that plugs into the bottom of the flash, and that will set of the 430ex whenever the camera's onboard flash fires, but that's a little clumsy. Or you can use the off camera synch cord. Or buy another EX flash (rather expensive). I have a dedicated slave flash that doesn't even have hotshoe contacts. It has an optical sensor built in, so I have my EX flash on my camera, set to manual and minimum power, and aim the head at the slave flash. Then I aim the slave and adjust the power and use that.