Moses Billings
With the development of the daguerreotype in the 1840s, the role of the portrait painter declined in general, because it was now much easier and much cheaper to have one's likeness presented in a visual format. While many portrait painters lost business in competition with the daguerreotype, Billings instead began to produce daguerreotype prints himself. It is not known exactly which prints were made by Moses Billings, as daguerreotypes were usually signed, when signed at all, along the side of the plate. Due to the traditional storing methods of daguerreotype plates, even this signature usually quickly became illegible. However, it has been generally noted, or at least hypothesized, that his daguerreotype prints showed a level of talent and artistry above that of amateur daguerreotypists. Though it is not known exactly which prints were his, it is known that he had largely abandoned the process by the 1850s. Even after he stopped making daguerreotypes, he did continue to paint people's portraits on canvas.
Henry Collen
Calotype was an early photographic process developed by Henry Fox Talbot who was a colleague of Collen's. Talbot supplied the photographic knowledge and Collen the artistic know-how. In an article titled "Photography in the 1840s," Peter Marshall describes the distinction between daguerreotypes and calotypes. "The daguerrotype spread rapidly around the world...There were some limitations on the spread." Daguerre's process was somewhat limited by his prior patent in the UK, and so only those professionals who could afford a license were able to do so. Meanwhile, Talbot patented his calotype process in the UK and the US, but he was unable to get a patent in France which also limited its growth. Also, Marshall states, "In general, most professional photographers used the daguerreotype process in the 1840s, while the calotype was generally favored by those who were not attempting to earn an income." (A chart describing the differences between calotypes and daguerreotypes is included in the Appendix).