Slave 55oex and 300d

[AlanL]

I want to know if is possible to trigger the 550ex flash off the camera, using the built in flash?

[rodbunn]

You can but you loose all the ETTL. You put a hot shoe "slave" on the
bottom of the 550. Why do this to a 550 though? It will be all manual
so why not use a cheap flash? Also, if the slave is all metal you have
to protect the 550's pins (except the center firing pin) otherwise the
550 freezes up between flashes.
Any flash around will fire it so you have to take that into consideration.

Good luck, Rod