Utilities

https://www.norwegiancreations.com/2018/07/controlling-a-camera-shutter-remotely-with-an-arduino/
I used this circuit with the 4N25 optocoupler: http://wei48221.blogspot.com/2016/06/how-to-use-4n25-optocoupler_27.html To use this with a 3.3V trigger signal, the resistor going to input 1 on the optocoupler should be around 50Ω.