Diffused lighting camouflage: Difference between revisions

| name =

| title =

| image = [[File:HMS Largs by night with incomplete Diffused Lighting Camouflage 1942.jpg|350px]]

| image_alt =

| sponsors =

| framework_programme =

| project_reference =

| location =

| participants =

| partners =

| budget =

| funding =

| website =

'''Diffused lighting camouflage''' was a form of [[active camouflage]] using [[counter-illumination]] to enable [[Ship camouflage|a ship to match its background]], the night sky, prototypedthat was tested by the [[Royal Canadian Navy]] on [[corvette]]s 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 ongoing [[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 so as, to make its brightness match its background. For this purpose, projectorsProjectors were mounted on temporary supports attached to the hull. Theand the prototype was developed to include automatic control of brightness using a [[photocell]]. The prototyped concept was never put into production, though the Canadian prototypes did briefly see service. The Canadian ideas were, however, adapted by the [[US Air Force]] in its [[Yehudi lights]] project.

[[File:Squid Counterillumination.png|thumb|PrincipleThe principle of counter-illumination camouflage in squid. When seen from below by a predator, the animal's light helps to match its brightness and colour to the sea surface.]]

In 1940, Edmund Godfrey Burr, a [[Canadian]] professor at [[McGill University]],<ref>R.C. Fetherstonhaugh, R.C., 1947, pages 337-341.</ref> serendipitously stumbled on the principle of counter-illumination, or as he called it "diffused-lighting camouflage".<ref>Burr, 1947, pages 45-54.</ref><ref>Burr, 1948, pages 19-35.</ref><ref>{{cite web |last1=Richard |first1=Marc |title=E. Godfrey Burr and his Contributions to Canadian Wartime Research: A Profile |url=http://fontanus.mcgill.ca/article/viewFile/179/201 |publisher=McGill University |accessdate=23 November 2015 |archiveurl=https://web.archive.org/web/20151123103141/http://fontanus.mcgill.ca/article/viewFile/179/201 |archivedate=23 November 2015}}</ref> Burr had been tasked by Canada's [[National Research Council (Canada)|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.<ref name="NavalMuseumQuebec"/>

===Royal CanadianPrototyping Navy===

The Admiralty report on the ''Trillium'' trials stated that "Under certain weather conditions, the Canadian trials, in spite of the crude equipment used, gave highly satisfactory results. The experience gained during the present trials indicated that in various other types of weather this same equipment gave a much less conclusive indication of its value", and described the technical difficulties that any future version would face.<ref>{{cite book |last1= |title=Clyde Trials on HMS ''Trillium'' |work=ADM/116/5026 Diffused Lighting |date=23 1941 |publisher=Admiralty |location=The National Archives, Kew}}</ref> The Admiralty informed the prime minister, [[Winston Churchill]], at the end of that month, stating that the "results seem quite promising".<ref>{{cite book |last1=First Lord of the Admiralty |title=Message to Prime Minister re DL Trials |work=ADM/116/5026 Diffused Lighting |date=30 March 1941 |publisher=Admiralty |location=The National Archives, Kew}}</ref>

TheChurchill Admiralty informedreplied the primenext ministerday, [[Winstonsuggesting Churchill]],that at"Surely theall endthis ofbusiness thatshould month,be statingpressed thatforward theon "resultsa seembroader front than the quiteone promisingship?".<ref>{{cite book |last1author=FirstChurchill, LordWinston of|author-link=Winston the AdmiraltyChurchill |title=Message to Prime Minister re DL Trials |work=ADM/116/5026 Diffused Lighting |date=30 March 1941 |publisher=Admiralty |location=The National Archives, Kew}}</ref>

Churchill replied the next dayAccordingly, suggestingin thatApril "Surely1941 allthe thisAdmiralty businessordered shouldfurther bedevelopment pressedwork forwardfor on a broader front than the"full onescale ship?trials".<ref>{{cite book |author=ChurchillFlag Officer-in-Charge, Winston |authorlink=Winston ChurchillNewcastle |title=MessageOrdertoPrimeCommanding MinisterOfficer reHMS DL Trials''Penelope'' |work=ADM/116/5026 Diffused Lighting |date=30 March 1941 |publisher=Admiralty |location=The National Archives, Kew}}</ref>

The British [[General Electric Company]] developed a manually operated diffused lighting system, which was trialled on the [[ocean boarding vessel]] [[HMS Largs|HMS ''Largs'']] and the [[light cruiser]] [[HMS Penelope (97)|HMS ''Penelope'']].<ref name="NavalMuseumQuebec"/> The ''Largs'' surface observation trials were conducted between 25 January and 6 February 1942; air observation trials, using [[Lockheed Hudson|Hudson bombers]], took place on the nights of 4/5 February and 25/26 March 1942. They found an average reduction in the range at which the ship could be seen at night from another ship of around 25% using binoculars, 33% using the naked eye;. theThe results from the air were less conclusive.<ref>{{cite book |last1=Admiralty |title=Trial Report D.L. 126: DL Trials on HMS ''Largs'' in Clyde Approaches |work=ADM/116/5026 Diffused Lighting |date=1942 |publisher=Admiralty |location=The National Archives, Kew}}</ref>

The best case was on the exceptionally clear moonless night of 29/30 January 1942, when ''Largs'' could be seen from a surface ship with the naked eye at {{convert|5250|yard|metre}} unlighted, but only {{convert|2250|yard|metre}} with her diffused lighting, a 57% reduction.<ref>{{cite book |last1=Admiralty |title=Trial Report D.L. 126: DL Trials on HMS ''Largs'' in Clyde Approaches |work=ADM/116/5026 Diffused Lighting |date=1942 |publisher=Admiralty |location=The National Archives, Kew}}</ref>

File:Diffused Lighting fittings on HMS Largs forward bridge.jpg|Diffused Lightinglighting type 3 fittings on HMS ''Largs'' forward bridge

File:Diffused Lighting fittings for HMS Largs.jpg|[[General Electric Company]]'s Diffuseddiffused Lightinglighting fittings for HMS ''Largs'': (from left to right) Type 3, Hull, Type 1, Type 2

File:Connection diagram for Diffused Lighting Camouflage of HMS Penelope.jpg|thumb|Connection diagram for [[HMS Penelope (97)|HMS ''Penelope'']], showing 60 diffused lighting fittings

The US Navy trialled an automatic system made by [[General Electric]]{{efn|Not the same company as the British GEC.}} of [[New York (state)|New York]] on the supply ship [[USS Hamul|USS ''Hamul'']], but halted research in 1942. The US Navy sent its control system and diffused lighting fittings to Canada's NRC, which installed it on the corvettes [[HMCS Edmundston (K106)|HMCS ''Edmundston'']] and [[HMCS Rimouski (K121)|HMCS ''Rimouski'']] in 1943 and carried out further prototyping.<ref name="NavalMuseumQuebec"/><ref>Summary Technical Report of Division 16, NDRC. Volume 2: Visibility Studies and Some Applications in the Field of Camouflage. (Washington, D.C.: Office of Scientific Research and Development, National Defense Research Committee, 1946), pagespp. 14-1614–16, and 225-241225–241</ref>

File:USS Hamul plan for Diffused Lighting.jpg|thumb|USS ''Hamul'' plan for Diffused Lighting camouflage fittings after the sea trials held on 3 January 1942

In September 1943, ''Rimouski'', using her diffused lighting system, but also some navigation lights, approached {{ship|German submarine|U-536}} in the [[Chaleur Bay|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 Rolf Schauenburg; ''U-536'' dived and escaped.<ref name="NavalMuseumQuebec"/> She was sunk two months later by the Canadian frigate {{HMCS|Nene|K270|2}} and corvette {{HMCS|Snowberry|K166|2}} on 19 November 1943 while she was attacking [[Convoy SL 139/MKS 30]].<ref>{{cite book |author=Kemp, Paul |title=U-Boats Destroyed: German Submarine Losses in the World Wars |publisher=Weidenfeld & Nicolson |year=1997 |page=158 |isbn= 978-1-557-50859-1}}</ref>

Following the Allied victory in the Battle of the Atlantic – through long-range aircraft, [[radar]], [[Enigma machine|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.<ref name="NavalMuseumQuebec"/>

[[File:Yehudi Lights Plan for B-24J-55-CO24 (cropped)Liberator.jpg|thumb|upright=1.3|The ''[[Yehudi lights|Yehudi]]'' counter-illumination system of automatically adjusted forward-pointing lights was trialled in [[Consolidated B-24 Liberator|B-24 Liberators]] from 1943 onwards.]]

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. However, British researchers found that the amount of electrical power required to camouflage an aircraft's underside in daylight was prohibitive, andwhile externally mounted light projectors disturbed the aircraft's aerodynamics.<ref name="NavalMuseumQuebec"/>

An American version, "[[Yehudi lights|Yehudi]]", using lamps mounted in the aircraft's nose and the leading edges of the wings, was trialled in [[Consolidated B-24 Liberator|B-24 Liberators]], [[Grumman TBF Avenger|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 counter-illumination camouflage with an affordable use of energy, more like that of marine animals than the Canadian diffused lighting approach.<ref name="NavalMuseumQuebec"/><ref name=NDRC>{{cite web | url=http://www.dtic.mil/dtic/tr/fulltext/u2/221102.pdf | archive-url=https://web.archive.org/web/20131023061821/http://www.dtic.mil/dtic/tr/fulltext/u2/221102.pdf | url-status=dead | archive-date=October 23, 2013 | work=Visibility Studies and Some Applications in the Field of Camouflage | publisher=Office of Scientific Research and Development, National Defence Research Committee | title=Camouflage of Sea-Search Aircraft | date=1946 | accessdateaccess-date=February 12, 2013 |last1=Bush, |first1=Vannevar |author1linkauthor1-link=Vannevar Bush |last2=Conant |first2=James |last3=Harrison |first3=George |display-authors=2 | pages=225–240}}</ref> But the system never entered active service, as [[radar]] became the principal means of detecting aircraft.<ref name="NavalMuseumQuebec"/>

* Fetherstonhaugh, R.C. ''McGill University at War: 1914–1918, 1939–1945''. (Montreal: McGill University, 1947), pagespp. 337–341. No ISBN.

* Hadley, Michael L. ''U-Boats Against Canada: German Submarines in Canadian Waters''. (Montreal: McGill-Queen's University Press, 1985), pagespp. 180–182. {{ISBN |978-0-773-50801-9}}.

* Lindsey, George R. ''No Day Long Enough: Canadian Science in World War II''. (Toronto: Canadian Institute of Strategic Studies, 1997), pagespp. 172–173. {{ISBN |978-0-919-76965-6}}.

* Pickford, R.J. ''Sublieutenant 'Commando' and Young Corvette Skipper.'' Salty Dips, Volume 1 (Ottawa: Naval Officers' Association of Canada, 1983), pagespp. 4–5. No ISBN.

* Schuthe, George M. ''MLs and Mine Recovery.'' Salty Dips, volume 1 (Ottawa: Naval Officers' Association of Canada, 1983), pages p. 83. No ISBN.

* Summary Technical Report of Division 16, NDRC. Volume 2: ''Visibility Studies and Some Applications in the Field of Camouflage''. (Washington, D.C.: Office of Scientific Research and Development, National Defense Research Committee, 1946), pagespp. 14–16 and , 225–241. [Declassified August 2, 1960].

* Sumrall, Robert F. "Ship Camouflage (WWII): Deceptive Art". ''United States Naval Institute Proceedings''. February 1973. pagespp. 67–81.

* [[Conrad Hal Waddington|Waddington, C.H.]] ''O.R. in World War 2: Operational Research Against the U-Boat''. (London: Elek Science, 1973), pages pp. 164–167. No ISBN.

[[Category:CamouflageCounter-illumination camouflage]]