Well this doesn't seem to be working.
Using the MATCHED INFRARED EMITTER AND PHOTOTRANSISTOR DETECTOR I thought this would work but no... it's not.
Video of the IR emitter emitting but nothing happening at the camera.
Image of the setup Arduino connected to camera by mini jack and wires.
Shorting the red and black wires causes the camera to take an exposure, but the photo-transistor doesn't seem to 'short' the circuit.