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 the camera
After Niépce's death in 1833, his partner Louis Daguerre continued to experiment and by 1837 had created the first practical photographic process, which he named the daguerreotype and publicly unveiled in 1839. Daguerre treated a silver-plated sheet of copper with iodine vapor to give it a coating of light-sensitive silver iodide. After exposure in the camera, the image was developed by mercury vapor and fixed with a strong solution of ordinary salt (sodium chloride). Henry Fox Talbot perfected a different process, the calotype, in 1840. As commercialized, both processes used very simple cameras consisting of two nested boxes. The rear box had a removable ground glass screen and could slide in and out to adjust the focus. After focusing, the ground glass was replaced with a light-tight holder containing the sensitized plate or paper and the lens was capped. Then the photographer opened the front cover of the holder, uncapped the lens, and counted off as many minutes as the lighting conditions seemed to require before replacing the cap and closing the holder. Despite this mechanical simplicity, high-quality achromatic lenses were standard.