Silver and Sunlight: The Science of Early Photography

Daguerreotype of the 1843 Nantes flood

Daguerreotype of the 1843 Nantes flood by an unknown photographer. Courtesy of Charles Isaacs Photographs, inc., New York.

All of Europe blazed with rumors. What was the secret of the marvelous images created by an amateur inventor and his showman partner? The appointed day for the revelation was 19 August 1839 at a joint meeting of the Académie des Sciences and the Académie des Beaux-Arts at the Institut de France in Paris. The meeting room quickly filled and an excited crowd spilled out into the corridors, courtyard, and street. An eyewitness reported that “after a long wait, a door opens in the background and the first of the audience to come out rushes into the vestibule. ‘Silver iodide,’ cries one. ‘Quicksilver!’ shouts another, while a third maintains that hyposulfite of soda is the name of the secret substance.”

From its beginnings in the 19th century, photography was a curious hybrid. Practiced by amateurs and professionals (male and female alike), the new form of picture making combined art and science, optics and chemistry, and handcraft and industry in unexpected and unprecedented ways. Like the railroad and the telegraph, photography was a modern technological innovation, a product of the Industrial Revolution. But it also had an aura of wonder and mystery: the chemical activity that made an amazingly detailed image appear on a metal plate or a piece of paper seemed almost magical. How could silver and sunlight alone produce such “divine perfection,” as one critic described it?

Light and Lenses

The optical basis for photography is relatively simple. Since ancient times people have observed that light passing through a small hole or lens into a darkened room projects an upside-down image on the opposite wall, just as it does on the retina of the eye. By the 17th century this phenomenon became the basis of a portable artist’s tool known as the camera obscura (Latin for “dark room”). A wooden box was fitted with a lens for gathering light and sharpening the image, which was reflected onto frosted glass on top of the box and traced by an artist. The camera lucida, or “light room,” was a related apparatus—a multisided prism mounted on a vertical rod attached to a drawing board. When an artist peered through the prism, the image appeared to be projected on the paper, where it could be traced.

Such mechanical aids were no substitute for artistic skill. William Henry Fox Talbot, an English gentleman-scholar vacationing near Lake Como in Italy in 1833, attempted to use a camera lucida to draw the scenery but met with little success. As he later recalled, “When the eye was removed from the prism—in which all looked beautiful—I found that the faithless pencil had only left traces on the paper melancholy to behold.” He mused, “How charming it would be if it were possible to cause these natural images to imprint themselves durably, and remain fixed upon the paper!”