Full-spectrum and ultraviolet (UV) photography have become increasingly popular among paranormal investigators, largely because they offer access to parts of the electromagnetic spectrum that our eyes simply can't see. Some ghost hunters hope that by widening the band of light their camera can detect, they may catch phenomena that would otherwise go unnoticed.

Although the technology sounds advanced, the underlying idea is straightforward: most digital camera sensors can capture ultraviolet and infrared light as well as visible light. Manufacturers block this extra light by covering the sensor with a small filter to ensure accurate colours in normal photography, because in normal photography, the extra wavelengths of IR and UV tend to distort colours and reduce image clarity.

A full-spectrum camera is simply a camera where this filter has been removed, allowing the sensor to record everything from near-UV through visible light and into the near-infrared range. Nothing else changes. The lens, sensor...