If you are using trigger's be sure they can handle the load of a relay. Sony triggers for example only source about a milliamp. Too low for a relay that could turn on an actuator. The trigger would see the relay as a dead short in that case. I'd recommend using small relays like "reed" type as an intermediate step at the least. And you'd still have to ensure the current requirement is met. Otherwise you need a transistor. Unless the VP50 is designed to source more current...many aren't since they are expecting relatively high impedance loads.