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.
Charles Nègre
Delaroche encouraged the use of photography as research for painting; Nègre started with the daguerreotype process before moving on to calotypes. His "Chimney-Sweeps Walking", an albumen print taken on the Quai Bourbon in 1851, may have been a staged study for a painting, but is nevertheless considered important to photographic history for its being an early instance of an interest in capturing movement and freezing it forever in one moment.