Editing Microdot (section)

== History ==
[[File:MicrodotCamera.jpg|thumb|Mark IV microdot camera]]
[[File:March 2020 Microdot Object (49673631061).jpg|thumb|A doll used by a German spy to smuggle microdot photographs to [[Nazi Germany]] until the spy's arrest in 1942. ([[FBI]] collection)]]

In 1870 during the [[Franco-Prussian War]], [[Paris]] was under siege and messages were sent by [[carrier pigeon]]. Parisian photographer [[René Dagron]] used [[microfilm]] to permit each pigeon to carry a high volume of messages, as pigeons can carry little weight.<ref>Kipper, Gregory. ''Investigator's Guide to Steganography''. Boca Raton: Auerbach Publications, 2003. {{ISBN?}}</ref>

Improvement in technology since then has made even smaller miniaturization possible.<ref>{{Cite book | last= Hayhurst | first=J. D. | title= The Pigeon Post into Paris 1870–1871 | publisher= (privately published) | year= 1970 | url= http://www.cix.co.uk/~mhayhurst/jdhayhurst/pigeon/pigeon.html}}</ref>

At the 1925 [[International Congress of Photography]] in Paris, [[Emanuel Goldberg]] presented a method of producing extreme reduction microdots using a two-stage process. First, an initial reduced negative was made, then the image of the negative was projected from the eyepiece of a modified microscope onto a collodium emulsion where the microscope specimen slide would be. The reduction was such that a page of text would be legibly reproduced in an area of 0.01&nbsp;mm<sup>2</sup>. This density is comparable to the entire text of the Bible fifty times over in one square inch. Goldberg's "Mikrat" (microdot) was prominently reported at the time in English, French and German publications.<ref name="Buckland 2006">{{Cite book | url= http://www.ischool.berkeley.edu/~buckland/goldberg.html | last= Buckland | first= Michael | title= Emanuel Goldberg and His Knowledge Machine: Information, Invention, and Political Forces | series= New Directions in Information Management | publisher= Libraries Unlimited | year= 2006}}</ref><ref>{{cite journal |last1=Goldberg |first1=Emanuel |title=A new process of micro-photography |journal=British Journal of Photography |date=13 August 1916|volume=73|issue=3458|pages=462–465}}</ref><ref>{{cite book |last1=Stevens |first1=G. W. W. |title=Microphotography: Photography and photofabrication at extreme resolution |date=1968 |publisher=Chapman & Hall |location=London |page=46 |edition=2 nd}}{{ISBN?}}</ref>

A technique comparable to modern microdots for [[steganography|steganographic]] purposes was first used in Germany during the [[Interwar period]]. It was also later used by many countries to pass messages through insecure postal channels. Later microdot techniques used film with [[aniline]] dye, rather than [[silver halide]] layers, as this was even harder for counter-espionage agents to find.

A popular article on espionage by [[J. Edgar Hoover]] in the ''Reader's Digest'' in 1946 attributed invention of microdots to "the famous Professor Zapp at the Technical University Dresden".<ref>{{cite journal |last1=Hoover |first1=J. Edgar |title=The enemy's masterpiece of espionage |journal=Reader's Digest |date=1946 |volume=48 |issue=April |pages=1–6 }}</ref> This article was reprinted, translated, and widely and uncritically cited in the literature on espionage. There never was a Professor Zapp at that university;<ref>{{cite book |last1=White |first1=William |title=The microdot: History and application |date=1992 |publisher=Phillips Publications |location=Williamstown, NJ |pages=49–56 | isbn= 0932572197}}</ref> Hoover's Zapp has been wrongly identified with [[Walter Zapp]], inventor of the [[Minox]] camera, which was used by spies but did not make microdots. Hoover appears to have conflated Emanuel Goldberg, who was a professor in Dresden, with Kurt Zapp who, late in [[World War II]], was in Dresden and taught spies how to make microdots.<ref name="Buckland 2006"/>