Editing Lippmann plate (section)

[[File:Gabriel Lippmann Le Cervin 1891-1899.jpg|thumb|Early colour photograph (circa 1891–1899) by Lippmann of the [[Matterhorn]]]]

'''Lippmann process photography''' is an early [[color photography]] method and type of [[alternative process]] photography. It was invented by French scientist [[Gabriel Lippmann]] in 1891 and consists of first focusing an image onto a [[Photographic plate|light-sensitive plate]], placing the [[Photographic emulsion|emulsion]] in contact with a mirror (originally liquid [[Mercury (element)|mercury]]) during the [[Exposure (photography)|exposure]] to introduce [[wave interference|interference]], [[Photographic developer|chemically]] [[Photographic processing|developing]] the plate, inverting the plate and painting the glass black, and finally affixing a [[Prism (optics)|prism]] to the emulsion surface. The image is then viewed by illuminating the plate with light. This type of photography became known as '''interferential photography''' or '''interferometric colour photography''' and the results it produces are sometimes called '''direct photochromes''', '''interference photochromes''', or '''Lippmann photochromes''' (distinguished from the earlier so-called "[[Photochrom|photochromes]]" which were merely black-and-white photographs painted with color by hand).<ref name=Eder668,670-672>{{cite book | last = Eder | first = J.M. | title = History of Photography, 4th. edition |trans-title=Geschichte der Photographie| year = 1945 | orig-year =  1932 |  publisher = Dover Publications | location = New York | pages = 668, 670, 671, 672 | isbn = 0-486-23586-6}}</ref><ref>{{patent|US|6556992}}</ref> In French, the method is known as ''[[:fr:photographie interférentielle|photographie interférentielle]]'' and the resulting images were originally exhibited as ''des vues lippmaniennes''. Lippmann won the [[Nobel Prize in Physics]] in 1908 "for his method of reproducing colours photographically based on the phenomenon of interference".<ref name=NPsummary>{{Cite web |url=https://www.nobelprize.org/prizes/physics/1908/summary/ |title=The Nobel Prize in Physics 1908 |year=2024 |website=NobelPrize.org |publisher=Nobel Prize Outreach AB 2024 |location=Stockholm |access-date=26 October 2024}}</ref>

Images made with this method are created on a '''Lippmann plate''': a clear glass plate (having no [[anti-halation backing]]), coated with an almost transparent (very low silver halide content) [[emulsion]] of extremely fine grains, typically 0.01 to 0.04 micrometres in diameter.<ref>R.W.G. Hunt, ''The Reproduction of Colour'', 6th ed, p6</ref>
Consequently, Lippmann plates have an extremely high resolving power<ref>{{cite web |url=http://www.tpub.com/content/photography/14209/css/14209_56.htm |title=Emulsion Definition |website=www.tpub.com |access-date=12 January 2022 |archive-url=https://web.archive.org/web/20100724065137/http://www.tpub.com/content/photography/14209/css/14209_56.htm |archive-date=24 July 2010 |url-status=dead}}</ref> exceeding 400 lines/mm.