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42. Draper, "Process," 222.
43. Draper, "First Portrait," 4.
44. Ibid., 5.
45. Snelling, "Some Facts," 382. The reason that there was no depth of field in a photograph
taken with a lens with such a small difference in ratio of focal length (seven inches) to diameter
(five inches) is found in the following optical principle:
Hence this may be laid down as a general rule, that the focal distance of a lens must always be
twice greater than the diameter of its aperture; that is, the aperture of a lens must of necessity be
smaller than half the focal distance. . . . The aperture of the object-glass, . . . must follow the rule
laid down, as clearness necessarily depends on it.
David Brewster, Letters of Euler on Different Subjects in Natural Philosophy, Vol. 2
(New York: Harpers and Brothers, 1846), 344-45. Draper assumed that the readers of his article
would have simply known this as general knowledge.
46. Editor's description of Wolcott's plate, Humphrey's Journal 2 (1 June 1851): 52; see
also Alexander S. Wolcott, "Improvements in the Daguerreotype," American Repertory of
Arts, Sciences, and Manufacturers 1 (April 1840): 195 (hereafter cited as American
Repertory); see also n41.
47. Welling, Photography in America, 35. The original daguerreotype is now in the Prints
and Photographs Division, Library of Congress.
48. Root, Camera, 347.
49. Lossing, "Professor Morse," 584. This article contains a wonderful reproduction
of one of Morse's first daguerreian portraits. This image is apparently as early as the well-known
daguerreotype illustrated in Marcus Root's The Camera and the Pencil, yet appears
virtually unknown to photographic historians. The image depicts two young girls (one was
possibly Morse's daughter) wearing bonnets. Their eyes are closed in the illustration. According
to the article, the original daguerreotype depicted three people.
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