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| p.1 #2 · Canon triggered by on board Nikon flash |
Anything is possible if you throw enough time and money at it but there's no easy, practical way to do it and varies with models.
Putting the Canon flash in "dumb" manual mode (holding mode button for 2 sec until M flashes) will prevent it from sleeping and allow it to be fired with an optical or radio trigger when mounted in a hot shoe > PC accessory or (580exII has a PC connector and just needs cable). That takes care of the slave end. To fire the slave correctly the camera's flash must be able to fire only the main burst with pre-flash disabled.
All things considered it's simpler to fire the slave with a radio trigger and forget about the light from the camera which will be difficult to balance with the slave and create unflattering shadows in portrait mode, or bite the bullet financially and buy a second CLS compatible Nikon flash. In terms of ease of use and capabilities such as HSS the latter is the better solution. The other option would be upgrading the Nikon camera to one with commander mode flash.