Dark field principle
The dark field principle is an optical effect that is used in photography and microscopy , among other things . Due to the dark field principle, an underexposed negative appears as a positive against a dark background .
History and Development
The dark field principle was first described by John Herschel in 1839 .
Hamilton L. Smith took advantage of this effect when he developed the ferrotype , also known as tintype , in 1856 . This is a collodion wet plate negative that is produced using the direct positive photographic process : A black lacquered iron sheet is used as the layer support for the collodion emulsion , which serves as a background for the unique negative; the negative then appears as positive due to the dark field principle.
The following photographic processes use the dark field principle:
- All direct positive methods :
At the end of the 19th century, the Austrian chemist Richard Zsigmondy and the physicist Henry Siedentopf in Jena developed an ultramicroscope based on the dark field principle. By improving this principle, he constructed the immersion ultramicroscope in 1912, which was the first to make particles with a size of a millionth of a millimeter visible.
See also
Web links
- Entry on Richard Zsigmondy in the Austria Forum (in the AEIOU Austria Lexicon )
- http://www.ub.uni-konstanz.de/kops/volltexte/2003/993/pdf/kalkbrenner1.pdf - Characterization and manipulation of the plasmon resonance of a single gold nanoparticle (dissertation by Thomas Kalkbrenner, University of Konstanz, Mathematisch - Natural Science Section, Department of Physics; PDF file; 3.27 MB)
- Timo Mappes, Norbert Jahr, Andrea Csáki, Nadine Vogler, Jürgen Popp and Wolfgang Fritzsche: The Invention of the Immersion Ultramicroscope in 1912 - The Beginning of Nanotechnology? . In: Angewandte Chemie . 124, No. 45, 2012, pp. 11307-11375. doi : 10.1002 / anie.201204688 .
- Immersion ultrasonic microscope according to R. Zsigmondy with optics patented in 1912