This circuit is used to trigger a camera's electronic shutter circuit when a flash of lightning is present. This circuit would also work for photographing fireworks displays or other events involving flashes of light.

It uses a photo-darlington sensor that looks through the viewfinder, and triggers the camera when the light is bright enough.

Ok, just starting out, but I'm going to make a shutter control as described here: "Super Mini Switch - A RS60-E3 Replacement".

Parts I have so far:

From a broken Casio calculator: