It was the Chinese philosopher Mo-Ti, about 2,500 years ago, who first described the optical phenomenon he called a "collecting place." Light passing through a tiny hole in the wall of a darkened room would cast a full-color, upside-down image of what was outside on the opposite wall.
But it was not until 1826 that a French tinkerer, inventor and engineer named Joseph Nicephore Niepce figured out how to record the image and fix it permanently on a flat surface. When he did it for the first time, he called it a "retina." Today we call it photography.
Last week, scientists at the Getty Conservation Institute in Los Angeles announced they had figured out how Niepce made the rather pedestrian "heliograph" of a French farmyard, entitled "Poin de Vue du Gras," but known more familiarly today as "The First Photograph."
"Niepce left some scattered notes, talking about different processes he was testing," said Getty senior scientist Dusan Stulik, who led the project. "But even though people had talked about it, they didn't really have any idea how he did it."
In fact, added Institute Director Timothy P. Whalen, photo conservators, unlike their counterparts who work with paintings, are ill-supplied with the knowledge needed to practice their trade.
"You go down to the National Gallery [of Art], and the conservators there literally know what paintings are made of," Whalen said. "Photo conservators simply don't have that information."
The First Photograph arrived at the institute earlier this year from its permanent home at the Harry Ransom Humanities Research Center, at the University of Texas at Austin.
Until then, scientists had only a vague idea of the processes and chemicals Niepce used. They knew only that the photograph was an 8-inch-by-6 1/2-inch sheet of metal about 1/16th of an inch thick.
They also had seen the black box in which Niepce had made the picture, a device called a camera obscura, or "darkened room" -- a term of art probably invented during the Italian Renaissance to describe the phenomenon first recorded by Mo-Ti.
Through the centuries, scientists had come to understand that when light rays pass through a tiny aperture into a dark room, they do not disperse, but instead cross each other to reform an inverted, full-color image on the surface of the back wall. Aristotle studied the optics involved, and Leonardo's notebooks refer to the concept.
The Italians, deeply involved in developing perspective and other techniques that would define modern Western painting, were fascinated by the inverted image and the artistic help it could provide: Put a canvas on the back, trace the image and use it as a template for a painting.
But what if you could fix the image -- take a scene straight from nature, duplicate it on a plate and freeze it for all time? Stulik said Niepce first had the idea in 1798, but only worked on it exclusively beginning in 1816.
"To make a photograph, Niepce needed three things -- the camera obscura, a sensitive surface and a way to fix it," Stulik said. "It was very hard work, because he used all the materials he knew about that would change some of their properties when they were struck by light."
He tried silver chloride, the basis of modern photography. It would take the image, Stulik said, but Niepce couldn't figure out how to fix it. So in 1826, he turned to bitumen, a tarry, asphalt-like substance used by engravers to guard copper plate from the effects of acid.
For his photographic plate, Niepce chose pewter, a heavy alloy of tin and other metals. "It was better than pure tin," Stulik said, "because it could be polished, and Niepce needed a surface that would stay smooth beneath a liquid film." Stulik said his team used x-ray spectrometry to identify the metal as pewter.
Niepce coated the plate with a mixture of bitumen and oil of lavender, creating a slick, dark, liquid film that gave the polished pewter a slightly goldish cast. Then he put the plate 20 inches deep in the back of a 10-inch-by-10-inch camera obscura and set it in the window of the Gras farmhouse on a sunny day.
The box had a small aperture in which Niepce had fixed a convex lens to sharpen and focus the image as it projected onto the pewter plate. He left it in place for eight hours, and in the places where ultraviolet light from the sun's rays hit the film, the bitumen had hardened and become insoluble.
Would those layers remain in place when Niepce washed away the rest of the film? Niepce removed the plate in the afternoon and dipped it in a mixture of oil of lavender and petroleum oil.
"Those areas which were not exposed started to dissolve, but the hardened bitumen remained in place," Stulik said. "That was the magic moment. I can only imagine what he felt."
A negative image emerged, but by changing the angle in the light, just slightly, the positive could be seen. A chimney, a section of brick wall, a field, a horizon and a glaring band of white -- "it looks like two suns," Stulik said, because the sun was the only thing moving during the exposure.
Stulik noted that Niepce corresponded frequently with Louis Daguerre. Niepce met him through his optician, who made lenses for both men. The two inventors even signed a letter of partnership in early 1829, but the collaboration never bore fruit because Niepce died in 1833.
Daguerre went on to develop a new fixing method with mercury vapors, which enabled him to produce a photograph in 20 minutes instead of eight hours. Although he credited Niepce as co-developer of the photographic process, his images were always known as daguerreotypes.
Stulik said the institute team carefully examined the Gras landscape with a microscope for signs of deterioration or damage to the original image. It found the bitumen and its pewter surface surprisingly robust, even after 177 years.
"We were afraid there would be very severe oxidation of the bitumen layer or flaking or cracking," Stulik said. "But the surface oxidation is only slight and image layer is much more stable."
The team removed the photograph's gilded plaster-and-wooden frame, and is having it restored elsewhere at the institute. Then both plate and frame will be encased in a stainless steel box with a heavy glass viewport. The box will be filled with inert argon gas to fend off corrosion.
Stulik said the high point of the restoration occurred when the institute unveiled Niepce's photograph last week:
"All these people were photographing it, and videotaping it, and I couldn't help thinking that all the photographs we have on walls, in shoe boxes and in museums, and all the film we have, and all the television we have -- it all intersects here," Stulik said. "This picture is the mother of all the imaging technology ever made."
