Five Good Questions on Mr. Daguerre's Process (1849)

JF Ptak Science Books  Quick Post

Antoine Francois Jean  Claudet, (1797-1867), began experimenting with Daguerreotype in 1840, and soon became photographer in ordinary to the Queen, being among the very first to practice Daguerrian portraiture in London. . He was very innovative and successful, and contributed many inventions and improvements in the cause of early photography, and was one of the first to use the collodion process.  

In an article published in the Philosophical Magazine in 1849¹ Claudet asks some still-fundamental questions about photography that he feels are still unanswered. Asking questions out loud (so to speak) doesn't happen that often in scientific and tech publications like this, and when they do, it is worth taking a moment to notice them.

Claudet asks and answers the following important questions:

• "Although the Daguerreotype process has during the last ten years been investigated by a great number of philosophers, and brought to a considerable degree of perfection by a still greater number of practitioners, it may appear surprising that the principal phaenomena upon which this new art is founded, are still enveloped in a mysterious darkness.

1. What is the action of light on the sensitive coating?
   2. How does the mercurial vapour produce the Daguerreotype image?
   3. Which are the particular rays of light that impart to the chemical surface the affinity for mercury?
   4. What is the cause of the difference in achromatic lenses between the visual and photogenic foci? why do they constantly vary?
   5. What are the means of measuring the photogenic rays, and of finding the true focus at which they produce the image?

Notes:

1. Claudet, Antoine Francois Jean "Mr. Claudet's Researches on the Theory of the principal Phaenomena of Photography in the Daguerreotype Process”, in  The London, Edinburgh and Dublin philosophical magazine and journal of science.Series 3, volume 35, July-December 1849. 8vo, viii, 552pp, with the article on pp 374-385.

"French photographer and scientist, active in England. He became an influential London portrait photographer at his Adelaide Gallery studio, licensed by the inventors to practise both the daguerreotype and the calotype. Claudet's earliest significant technical contribution, in 1841, was in greatly increasing the sensitivity of the daguerreotype plate, thus reducing exposure times and making the process much more suitable for portraiture. In 1851 he moved to Regent Street, where he also began using the wet-plate process. Claudet published prolifically on photography, vision, and the photographic representation of sculpture. He was also one of the foremost early practitioners of stereoscopic photography, inventing a folding stereoscope and other devices. Many of Claudet's impressive photographs survive, but his collection of historical photographic incunabula was destroyed by fire after his death."-- The Oxford Companion to the Photograph

Also (among many other contributions) in the volume are:

• Hamilton, William Rowan. “Sir W. R. Hamilton on Quaternions; or on a New System of
  Imaginaries in Algebra” and “Sir W. R. Hamilton on Quaternions; or on a New System of Imaginaries in Algebra (continued)”;
• Hargreaves, C.J. “Mr. C. J. Hargreave's Analytical Researches concerning Numbers”;
• Becquerel, Antoine. “M. Becquerel on the Development of Electricity in the Act of Muscular Contraction”
• Forbes, James David (pioneer in the study of glaciers). “Prof. J. D. Forbes on an Experiment to determine the Earth's Density”
• Grove, William R. “Mr. W. R. Grove on the Effect of surrounding Media on Voltaic Ignition “
• “The Rev. B. Bronwin on the Theory of the Tides “ and “Rev. B. Bronwin on the Theory of the Tides (continued)” and “The Rev. B. Bronwin on the Theory of the Tides (concluded)”;
• Lubbock, John W. “Sir J. W. Lubbock on Shooting Stars”