Daguerreotype
It is said that Daguerre has found the means to collect, on a plate prepared by him, the image produced by the camera obscura, in such a way that a portrait, a landscape, or any view, projected upon this plate by the ordinary camera obscura, leaves an imprint in light and shade there, and thus presents the most perfect of all drawings ... a preparation put over this image preserves it for an indefinite time ... the physical sciences have perhaps never presented a marvel comparable to this one.
A further clue to fixing the date of invention of the process is that when the Paris correspondent of the London periodical "The Athenaeum" reported the public announcement of the daguerreotype in 1839, he mentioned that the daguerreotypes now being produced were of considerably better quality than the ones he had seen "four years earlier".
History of photographic lens design
Charles Chevalier's Paris optical firm produced lenses for both Niépce and Daguerre for their experiments in photography. In 1829, Chevalier created an achromatic lens (a two-element lens made from "crown glass" and "flint glass") to cut down on chromatic aberration for Daguerre's experiments. Chevalier reversed the lens (originally designed as a telescope objective) to produce a much flatter image plane and modified the achromat to bring the blue end of the spectrum to a sharper focus. Reversing the lens caused severe spherical aberration so a narrow aperture stop was necessary in front of the lens. On 22 June 1839, Daguerre contracted Alphonse Giroux (France) to manufacture his daguerreotype apparatus. The Giroux Le Daguerreotype camera used an almost 16-inch (40 cm) focal length reversed achromatic lens with a f/16 stop in front of it made by Chevalier to take 6½×8½ inch (about 16.5×21.5 cm) images.