Daguerreotype
Morse met the inventor of the daguerreotype, Louis-Jacques-Mande Daguerre, in Paris in January 1839 when Daguerre's invention was announced [2]. While the daguerreotype fascinated Morse, he was concerned about how the new invention would compete with his telegraph. However, Morse's viewing of the daguerreotype alleviated his fears when he saw how revolutionary its technology was. Morse wrote a letter to his brother Sidney describing Daguerre's invention, which Sidney then published in the New-York Observer on April 20, 1839. While this was not the first report of the daguerreotype to appear in America, it was the first in-person report to appear in the United States.
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.