page_title: Yehudi lights
section_title: Canadian origins
hierarchical_section_title: Yehudi lights / Canadian origins
context_page_description: Yehudi lights are lamps of automatically-controlled brightness placed on the front and leading edges of an aircraft to raise the aircraft's luminance to the average brightness of the sky, a form of active camouflage using counter-illumination. They were designed to camouflage the aircraft by preventing it from appearing as a dark object against the sky.
  The technology was developed by the US Navy from 1943 onwards, to enable a sea-search aircraft to approach a surfaced submarine to "within 30 seconds of flying time" before becoming visible to the submarine's crew. This in turn enabled the aircraft to engage the submarine with depth charges before it could dive, to counter the threat from German submarines to allied shipping. The concept was based on earlier research by the Royal Canadian Navy in its diffused lighting camouflage project.
  Yehudi lights did not come into operational usage and were considered obsolete with postwar advances in radar. With more recent improvements in stealth technology, Yehudi lights have again attracted interest.
context_section_description: The use of Yehudi lights to camouflage aircraft by matching their luminance with the background sky was developed, in part, by the US Navy's Project Yehudi from 1943 onwards, following pioneering experiments in the Canadian diffused lighting camouflage project for ships early in the Second World War. A Canadian professor, Edmund Godfrey Burr, had serendipitously stumbled upon the principle when he saw an aircraft coming in to land over snow suddenly vanish; he realized that the reflected light had increased its brightness just enough to match the background sky. The ships were fitted with ordinary projectors mounted on small platforms fixed to their sides, with the projectors pointing inwards at the ship's side. The brightness was adjusted to match the brightness of the sky. The Canadian experiment showed that such counter-illumination camouflage was possible, arousing interest in both Britain and America, but the equipment was cumbersome and fragile, and neither the Royal Canadian Navy nor their allies brought it into production.
caption: Maritime patrol Catalina, painted as bright as possible—white—to minimise visibility against the sky, still mainly appears dark. Yehudi lights provide better brightness matching by generating light.