IT consultant and photo enthusiast Viktor Takacs didn’t have much success when he tried capturing lightning on camera, so he decided to build this fancy do-it-yourself trigger (which he named “Zeus”) that automatically snaps a photo whenever the photodiode detects a flash of lightning. He even built a knob into the device that can be used to adjust sensitivity. The demo above shows the trigger reacting to manually triggered flashes from a strobe.
Takacs has a detailed post that walks through how he created the device. You can also email him for the code used by the microcontroller.