Diffused lighting camouflage Diffused lighting camouflage was a form of active camouflage using counter - illumination to match the background , prototyped by the Royal Canadian Navy during World War II . Concept . 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 cephalopod s 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 diffusely lighting out the animal ' s shadow . In 1940 , a Canadian professor at McGill University , Edmund Godfrey Burr , serendipitously stumbled on the principle of counterillumination , 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 . Burr wondered if he could camouflage planes by somehow reducing this difference in brightness . One night in December 1940 , Burr saw a plane coming in to land over snow suddenly vanish : light reflected from the snow had illuminated the underside of the plane just enough to cancel out the difference in brightness , camouflaging the plane perfectly . Burr informed the NRC , who told the RCN . They realized that the technique could help to hide ships from German submarines in the Battle of the Atlantic . Before the introduction of centimetre radar , submarines with their small profile could see convoy ships before they were themselves seen . Diffused lighting camouflage might , the RCN believed , redress the balance . Prototyping . Burr was quickly called to Canada ' s Naval Services Headquarters to discuss how to apply diffused lighting camouflage . Simple tests in the laboratory served as proof of concept . In January 1941 , sea trials began on the new corvette HMCS " Cobalt " . She was fitted with ordinary light projectors — neither designed for robustness , nor waterproofed — on temporary supports on one side of the hull ; brightness was controlled manually . The trial was sufficiently promising for a better prototype to be developed . The second version , with blue - green filters over the projectors , was trialled on board HMCS " Chambly " in May 1941 . This gave better results as the filters removed the reddish bias to the lamps when at low intensity ( lower colour temperature ) . The supports too were retractable , so the delicate projectors could be stowed away for protection when not in use . This second version reduced " Chambly ' s " visibility by 50 % in most conditions , and sometimes by as much as 75 % . This was enough to justify development of a more robust version . The third version featured a photocell to measure the brightness of the night sky and the ship ' s side ; the projectors ' brightness was automatically controlled to balance out the difference . It was tested in September 1941 on the corvette HMCS " Kamloops " . Parallel trials of the Canadian diffused lighting equipment were carried out in March 1941 by the Royal Navy on the corvette HMS " Trillium " ; later in 1941 , the Royal Navy trialled the General Electric Company ' s manually operated diffused lighting system on HMS " Largs " , and then halted the research . The US Navy trialled an automatic system made by General Electric of New York ( a different company ) in 1942 , but soon also halted research . The US Navy sent its control system and projectors to Canada ' s National Research Council , which installed it on HMCS " Edmundston " and HMCS " Rimouski " in 1943 . Active service . Both " Edmundston " and " Rimouski " were fitted with about 60 light projectors : those on the hull were on retractable supports ; those on the superstructure were on fixed supports . Each ship ' s diffused lighting system was tested systematically in St Margaret ' s Bay , and then trialled when actually escorting Atlantic convoys in 1943 . Experimentally , the diffused lighting reduced the ships ' visibility by up to 70 % , but at sea the electrical equipment proved too delicate , and frequently malfunctioned . Worse , the system was slow to respond to changes in background lighting , and the Canadian Navy considered the lighting too green . In September 1943 , " Rimouski " , using her diffused lighting system , but also some navigation lights , approached in the Baie des Chaleurs . The intention was to make Rimouski appear as " a small and inoffensive ship " in an operation to trap the submarine , and this appears to have worked as the U - boat did not detect her . However the attack failed , as a wrong signal sent from shore alerted the submarine ' s commander , Kapitänleutnant Schauenburg ; " U - 536 " dived and escaped . She was sunk two months later by the Canadian corvettes " Nene " and on 19 November 1943 while she was attacking Convoy SL 139 / MKS 30 . Following Allied victory in the Battle of the Atlantic — through longer - range aircraft , radar , code decryption , and better escort tactics — the need to camouflage ships from submarines greatly decreased , and diffused lighting research became a low priority . The work was halted when the war ended . In aircraft . Because submarines at the surface could see the dark shape of an attacking aircraft against the night sky , the principle of diffused lighting camouflage also applied to aircraft . British researchers found that the amount of electrical power required to camouflage an aircraft ' s underside in daylight was prohibitive ; and externally mounted light projectors disturbed the aircraft ' s aerodynamics . An American version , " Yehudi " , using lamps mounted in the aircraft ' s nose and the leading edges of the wings , was trialled in B - 24 Liberators , Avenger torpedo bombers and a Navy glide bomb from 1943 to 1945 . By directing the light forwards towards an observer ( rather than towards the aircraft ' s skin ) , the system provided effective counterillumination camouflage , more like that of marine animals than the Canadian diffused lighting approach . But the system never entered active service , as radar became the principal means of detecting aircraft .