Editing Camouflage (section)

=== Counter-illumination ===

{{main|Counter-illumination}}

[[File:Squid Counterillumination.png|thumb|Principle of [[counter-illumination]] in the [[Watasenia scintillans|firefly squid]]]]

Counter-illumination means producing light to match a background that is brighter than an animal's body or military vehicle; it is a form of active camouflage. It is notably used by some species of [[squid]], such as the [[Watasenia scintillans|firefly squid]] and the [[Abralia veranyi|midwater squid]]. The latter has light-producing organs ([[photophores]]) scattered all over its underside; these create a sparkling glow that prevents the animal from appearing as a dark shape when seen from below.<ref name="Abralia with photo">{{cite web |url=http://ocean.si.edu/ocean-photos/midwater-squid-abralia-veranyi |title=Midwater Squid, Abralia veranyi |publisher=Smithsonian National Museum of Natural History |access-date=28 November 2011}}</ref> Counterillumination camouflage is the likely function of the [[bioluminescence]] of many marine organisms, though light is also produced to attract<ref>{{cite journal |last=Young |first=Richard Edward |title=Oceanic Bioluminescence: an Overview of General Functions |journal=Bulletin of Marine Science |date=October 1983 |volume=33 |issue=4 |pages=829–845 |url=http://www.ingentaconnect.com/content/umrsmas/bullmar/1983/00000033/00000004/art00003}}</ref> or to detect prey<ref>{{cite journal |last1=Douglas |first1=R. H. |last2=Mullineaux |first2=C. W. |last3=Partridge |first3=J. C. |title=Long-wave sensitivity in deep-sea stomiid dragonfish with far-red bioluminescence: evidence for a dietary origin of the chlorophyll-derived retinal photosensitizer of Malacosteus niger |journal=Philosophical Transactions of the Royal Society B |date=September 2000 |volume=355 |issue=1401 |pages=1269–1272 |pmc=1692851 |doi=10.1098/rstb.2000.0681 |pmid=11079412}}</ref> and for signalling.

Counterillumination has rarely been used for military purposes. "[[Diffused lighting camouflage]]" was trialled by Canada's [[National Research Council (Canada)|National Research Council]] during the Second World War. It involved projecting light on to the sides of ships to match the faint glow of the night sky, requiring awkward external platforms to support the lamps.<ref name="NavalMuseumQuebec">{{cite web |title=Diffused Lighting and its use in the Chaleur Bay |url=http://www.navy.forces.gc.ca/navres/NMQ_MNQ/researches_recherches/diffusedLighting_camouflageLumineux/index-eng.asp |access-date=3 February 2013 |work=Naval Museum of Quebec |publisher=Royal Canadian Navy |archive-url=https://web.archive.org/web/20130522231113/http://www.navy.forces.gc.ca/navres/NMQ_MNQ/researches_recherches/diffusedLighting_camouflageLumineux/index-eng.asp |archive-date=22 May 2013}}</ref> The Canadian concept was refined in the American [[Yehudi lights]] project, and trialled in aircraft including [[Consolidated B-24 Liberator|B-24 Liberators]] and naval [[Grumman TBF Avenger|Avengers]].<ref name="Hambling">{{cite magazine |last=Hambling |first=David |title=Cloak of Light Makes Drone Invisible? |magazine=Wired |date=9 May 2008 |url=https://www.wired.com/dangerroom/2008/05/invisible-drone |access-date=17 June 2012}}</ref> The planes were fitted with forward-pointing lamps automatically adjusted to match the brightness of the night sky.<ref name="NavalMuseumQuebec"/> This enabled them to approach much closer to a target – within {{Convert|3000|yards}} – before being seen.<ref name="Hambling"/> Counterillumination was made obsolete by [[radar]], and neither diffused lighting camouflage nor Yehudi lights entered active service.<ref name="NavalMuseumQuebec"/>

<gallery class="center" mode="nolines" heights="150px" widths="150px">
File:HMS Largs by night with incomplete Diffused Lighting Camouflage 1942.jpg|[[HMS Largs|HMS ''Largs'']] by night with incomplete [[diffused lighting camouflage]], 1942, set to maximum brightness
File:HMS Largs bulwark with Diffused Lighting Camouflage fittings.jpg|Bulwark of HMS ''Largs'' showing 4 (of about 60) diffused lighting fittings, 2 lifted, 2 deployed
File:Principle of Yehudi Lights with Avenger head-on view.jpg|[[Yehudi Lights]] raise the average brightness of the plane from a dark shape to the same as the sky.
</gallery>