Editing Lippmann plate (section)

==Method==
[[File:Colodión húmedo, collodion wet plate process, el colodión se vierte en una placa de vidrio, IPCE, Madrid, España.jpg|thumb|right|alt=An artist wearing gloves pours liquid salt collodion onto a glass plate.|To create a Lippmann plate, a [[Photographic emulsion|light-sensitive emulsion]] of [[silver halide]] dispersed in [[gelatin]] is coated onto a glass [[photographic plate]] ''(Shown here: [[collodion|collodion solution]])''. Later, the back is painted black and a prism is glued to the front to control reflection.]]
In Lippmann's method, a glass plate is coated with an ultra fine grain<ref>"[http://spiedigitallibrary.org/proceedings/resource/2/psisdg/3358/1/95_1?isAuthorized=no Recent developments in Lippman photography"], Jean-Marc Fournier, Benjamin R. Alexander, et al.;Proc. SPIE 3358, 95 (1998)</ref> light-sensitive film (originally using the [[Albumen print|albumen process]] containing [[potassium bromide]]; later and primarily using [[Gelatin silver print|silver halide gelatin]]),<ref name=HOP>{{cite journal |last1=Bjelkhagen |first1=Hans |date=19 Jan 2015 |title=Lippmann photography: Reviving an early colour process |url=https://www.tandfonline.com/doi/abs/10.1080/03087298.1999.10443331 |journal=[[History of Photography (journal)|History of Photography]] |publisher=[[Taylor & Francis]] |doi=10.1080/03087298.1999.10443331 |url-access=subscription |access-date=26 October 2024}}</ref> then dried, sensitized in the silver bath, washed, irrigated with cyanine solution, and dried again. The back of the film is then brought into optical contact with a reflective surface. This originally was done by mounting the plate in a specialized holder with pure [[mercury (element)|mercury]] behind the film. When it is exposed in the camera through the glass side of the plate, the light rays which strike the transparent light-sensitive film are reflected back on themselves and, by interference, create [[standing wave]]s.<ref name=Eder668,670-672/> The standing waves cause exposure of the emulsion in diffraction patterns. The developed and fixated diffraction patterns constitute a [[Bragg diffraction|Bragg condition]] in which diffuse, white light is scattered in a specular fashion and undergoes constructive interference in accordance to Bragg's law.<ref>[[Bragg diffraction]]</ref> The result is an image having very similar colours as the original using a black and white photographic process.

For this method Lippmann won the [[Nobel Prize in Physics]] in 1908.<ref>{{cite web |url=http://nobelprize.org/nobel_prizes/physics/articles/biedermann/index.html |title=Lippmann's and Gabor's Revolutionary Approach to Imaging |website=nobelprize.org |url-status=dead |archive-url=https://web.archive.org/web/20060712011307/http://nobelprize.org/nobel_prizes/physics/articles/biedermann/index.html |archive-date=2006-07-12}} </ref>

The colour image can only be viewed in the reflection of a diffuse light source from the plate, making the [[field of view]] limited, and therefore not easily copied with conventional techniques. The method was very insensitive with the emulsions of the time and it never came into general use. Another reason Lippmann's process of colour photography did not succeed can be found in the invention of the [[Autochrome Lumière|autochrome plates]] by the [[Lumière brothers]].<ref name=Eder668,670-672/> A technique derived from the Lippmann technique has been proposed as a method of producing images which can easily be viewed, but not copied, for security purposes.<ref>{{Cite web |url=http://holowiki.nss.rpi.edu/wiki/Lippmann_Security |title=Optically Variable Device for Security Documents |last1=Bjelkhagen |first1=Hans |url-status=dead |archive-url=https://web.archive.org/web/20211021022005/http://holowiki.nss.rpi.edu/wiki/Lippmann_Security |archive-date=21 October 2021}}</ref>