my brother wagers he could use his nikon d90 to trigger my canon 580EXII flash, just using the pop up flash. wouldn't be ettl but just manual. i said i hadn't heard this was possible... what does the fm community say? possible or pipe dream? thanks very much!! --rowdy
It's my understanding that the 580EXII does not have an optical trigger built in. However, you can certainly purchase an optical trigger that plugs into the PC sync port and trigger it that way. This Green Trigger is what you would need to make it work.
Most of the higher end Nikon flashes have an optical trigger mode called SU-4. So your brother might assume that the Canon flashes also have this type option built in.