This slave unit is designed for use with digital cameras that produce multiple flashes before taking a picture (pre-flashes).
Just plug the slave unit into your flashgun and you are almost ready to shoot! Most digital cameras work first time with the default settings of the Firefly 3. In other cases you can use the learning feature of this unit to train for your camera's unique sequence of flashes. Once learnt the attached flashgun will go off on the last flash each time for a perfect shot.
If you do not want to use the illumination from the camera flashgun, to avoid "misty" pictures, then you can tape the infra red filter provided to the camera flash window to provide an infra red only flash. The slave unit will be triggered, but no visible light will come from the trigger flashgun.