Video feedback loops - the method pioneered by Klaus Schreiber - are one of the most recognisable and enduring methods in visual ITC.

A video feedback loop is created when the live output from a camera is routed to a monitor or television, and the camera is then pointed at that same display. The camera captures the screen, the screen displays what the camera sees, the loop continues.

The system starts generating a stream of continuously changing, abstract imagery that evolves in real time. These patterns can range from swirling textures and geometric shapes to what some early researchers described as fleeting faces or shadowy figures. The idea is to watch these shapes either in real time, or frame-by-frame later, and look for recognisable forms or momentary images.

Because feedback loops work in real time, investigators can watch the output while adjusting the camera's angle or lens settings. Even the smallest change in...