Difference between revisions of "Daguerreotype Process"

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|image_text= 1840s [[Le_Daguerreotype|Daguerreotype camera]]<br>in the [http://americanhistory.si.edu/collections/subject_detail.cfm?key=32&colkey=25 Smithsonian Museum of American History]
 
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The '''Daguerreotype''' was the World's first practical photographic system. The process was invented by French artist &amp; scientist [[Louis Jacques Mandé Daguerre|Louis Daguerre]] over a long period between 1821-1837. Daguerre gave the rights to use the process, in exchange for a pension, to the French government in 1839; the government gave the rights "free to the World".
 
The '''Daguerreotype''' was the World's first practical photographic system. The process was invented by French artist &amp; scientist [[Louis Jacques Mandé Daguerre|Louis Daguerre]] over a long period between 1821-1837. Daguerre gave the rights to use the process, in exchange for a pension, to the French government in 1839; the government gave the rights "free to the World".

Revision as of 15:41, 10 August 2008

The Daguerreotype was the World's first practical photographic system. The process was invented by French artist & scientist Louis Daguerre over a long period between 1821-1837. Daguerre gave the rights to use the process, in exchange for a pension, to the French government in 1839; the government gave the rights "free to the World".

The Images

The Daguerreotype is a positive image made on a metal plate, with each image made by a separate exposure in the camera. The process was capable of very fine detail and subtle tones. The system was cheap enough to allow many people access to photographs of family members. In a very short time, Daguerreotype studios proliferated across the World; New York City is said to have had over 70 by 1850.

The process

There are five stages in making a Daguerreotype:

  1. Plate Preparation: a copper sheet is plated with silver (by Sheffield plating, or, later, by electroplating); this is then polished to a very high gloss.
  2. Sensitisation: the plate is placed in an iodizing box and exposed to iodine vapour until all the surface silver has been converted to silver iodide, turning the plate orange. This is the light-sensitive coating. This had to be done shortly before the exposure, as iodized plates would rapidly degrade.
  3. Exposure: The plate is loaded into a camera, and an exposure made simply by removing the lens cap. Exposures in early cameras could be over twenty minutes, even in bright daylight! However, this was less than some other, earlier processes. In 1840, Englishman John Goddard showed that sensitivity could be increased by using bromine, as well as iodine; this, together with improving lens technology brought times down considerably. Petzval's lens in particular brought typical apertures down from ~f14 to ~f3.5 - four stops improvement, i.e. potentially 16 times shorter exposures.
  4. Development: the plates, kept in the dark, are suspended over a bath of mercury, which is heated to 60°C (140°F); mercury vapour forms an amalgam with the exposed silver iodide.
  5. Fixing: unexposed silver iodide, not amalgamated with mercury, is washed off the plate using a salt (sodium chloride) solution (later replaced by weak sodium thiosulphate solution). This leaves the mercury/silver amalgam highlights and shadows of the original silver as a permanent - but delicate - image. This image would sometimes be toned with gold chloride. The plate was usually sealed into a glass-fronted frame to protect the fragile surface from being scratched, or oxidising (tarnishing to black, as silver cutlery does) in the air.

Disadvantages

The Daguerreotype had several problems:

  • There was no negative; individual exposures made only one Daguerreotype - copies or enlargements were not possible except by photographing a new, inferior, Daguerreotype of the original. Some Daguerreotypes were engraved to make printing plates. Daguerre himself hindered professor Alfred Donné's introduction of a more sophisticated etching method for making printing plates from Daguerreotypes.
  • Long - or very long - exposure times - made sharp images of people almost unattainable with early lenses & plates.
  • The photograph had to be viewed in good light, and carefully angled to be seen well; viewing at the wrong angle made the image appear as a negative.
  • The plates were not transparent and so the image is viewed from the same side as the lens - hence the picture is normally left-right reversed. Some cameras incorporated a mirror to correct this during exposure - but most Daguerreotypes are "mirror images".
  • The silver plates and processing (and the individual exposure/processing cycle for each picture) were expensive.
  • The process involved highly poisonous bromine & mercury vapours.

However, in spite of these drawbacks, Daguerreotypes were popular and the process spread across the world. One exception was in the British Empire; whilst the French government had given rights to the World, the Daguerreotype had been patented in Britain and hence its colonies - which encouraged use of many other processes. Talbot's Calotype negative process rivalled the Daguerreotype process, but Daguerreotypes were generally preferred for portraiture, the main subject of the 1840s' photography.

Daguerreotype photography continued until the late 1850s - particularly in France - until largely replaced by the Ambrotype process or other positive variants of Archer's wet-collodion process, originally a negative process that also replaced the Calotypes.

Sources

  • The Focal Encyclopedia of Photography, Focal Press/Elsevier, 4th ed., 2007
  • Coe, Brian, Cameras, from Daguerreotypes to Instant Pictures, Norbok, 1978
  • Coe, Brian, The Birth of Photography, Ash & Grant, 1976
  • Neher, Frank Ludwig Die Erfindung der Photographie, Stuttgart 1938

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