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".
Louis Désiré Blanquart-Evrard
He was born and raised in Lille where he studied chemistry with Charles Frédéric Kuhlmann and miniature painting on porcelain. After Louis Daguerre solved the problem of long exposure time and introduced daguerreotypy, a practical photographic process, to the general public in 1839, Blanquart-Evrard developed interest in photography. He studied the "calotype", salt-print negative process, and in 1847 became the first person to publish on negative/positive paper photo process in France. He developed a method of bathing the paper in solutions of potassium iodide and silver nitrate rather than brushing these chemical baths on the surface. In January 1847, he presented his research on stabilizing the photo prints by floating them in the silver solution to the French Academy of Sciences.