Diffused lighting camouflage

Diffused lighting camouflage was a form of active camouflage using counter-illumination to enable a ship to match its background, the night sky, that was tested by the Royal Canadian Navy on corvettes during World War II. The principle was discovered by a Canadian professor, Edmund Godfrey Burr, in 1940. It attracted interest because it could help to hide ships from submarines in the Battle of the Atlantic, and the research project began early in 1941. The Royal Navy and the US Navy carried out further equipment development and trials between 1941 and 1943. The concept behind diffused lighting camouflage was to project light on to the sides of a ship, to make its brightness match its background. Projectors were mounted on temporary supports attached to the hull and the prototype was developed to include automatic control of brightness using a photocell. The concept was never put into production, though the Canadian prototypes did briefly see service. The Canadian ideas were adapted by the US Air Force in its Yehudi lights project. Diffused lighting camouflage was explored by the Royal Canadian Navy (RCN) and tested at sea on corvettes during World War II, and later in the armed forces of the UK and the US. An equivalent strategy, known to zoologists as counter-illumination, is used by many marine organisms, notably cephalopods including the midwater squid, Abralia veranyi. The underside is covered with small photophores, organs that produce light. The squid varies the intensity of the light according to the brightness of the sea surface far above, providing effective camouflage by lighting out the animal's shadow. In 1940, Edmund Godfrey Burr, a Canadian professor at McGill University, serendipitously stumbled on the principle of counter-illumination, or as he called it "diffused-lighting camouflage". Burr had been tasked by Canada's National Research Council (NRC) to evaluate night observation instruments. With these, he found that aircraft flying without navigation lights remained readily visible as silhouettes against the night sky, which was never completely black.