the few surviving masterpieces from the earliest days of color photography, made using a process dev

Almost as intriguing as the pictures themselves, however, is the story of how they recently made their way from a house in Buffalo, where they apparently sat unseen for decades, to the collection of the George Eastman House in Rochester, one of the world’s leading photography museums, where they will be exhibited for the first time this fall.

Eastman House has a substantial collection of Steichen works, including 22 of the same kind of color photographs, known as autochromes. But when Anthony Bannon, the museum’s director, received a call last summer from a Buffalo lawyer, who said his client, Charlotte Albright, a 96-year-old painter, wanted to donate three examples of what were probably antique glass-plate negatives, Mr. Bannon assumed they were the works of her mother, Charlotte Spaulding.

That would have been an important find in itself. Spaulding had a brief career as a photographer and member of the influential scene known as the Photo Secession, led by Steichen and Alfred Stieglitz. Then she put down her camera for good in 1910 after marrying Langdon Albright, the son of a prominent Buffalo industrialist, John J. Albright, an early benefactor of what is now the Albright-Knox Art Gallery in Buffalo.

In August Mr. Bannon drove to Buffalo to meet the lawyer, Robert J. Plache. Because of the two men’s erratic schedules, they arranged on the fly to meet in the parking lot of an ice cream parlor in a Buffalo suburb, where Mr. Plache emerged from his car with a plastic-wrapped package.

Upon opening it, Mr. Bannon saw that one item inside was a Spaulding glass-plate negative. Then, almost immediately, he realized that the other two 5-by-7-inch pieces of glass, portraits of a beautiful young woman in an Edwardian gown and pearls, were not.

They were Steichens, one of them signed.

“And I said, ‘Thank you very much,’ ” Mr. Bannon recalled dryly in a recent interview.

Steichen was hugely influential during his lifetime, serving for almost two decades as the director of photography at the Museum of Modern Art. Although his reputation dimmed after his death in 1973, it has surged back. In February 2006 one of his platinum prints, “The Pond — Moonlight,” made in 1904, set an auction record for a photograph, selling for almost $3 million at Sotheby’s in New York.

“It is so rare that one has a chance to add imagery to an artist’s oeuvre, never mind one of the stature of Steichen,” Mr. Bannon said. “You think the ground has been pretty well covered, and then you find something like this.”

Mr. Plache, speaking on behalf of Mrs. Albright, said that she was unable to conduct an interview about the photographs, which probably came into her possession after her mother’s death in 1939. But as far as anyone associated with Mrs. Albright knows, she never displayed them and they were kept in a cupboard or closet in her house for decades. It is unclear whether she knew that two of the plates were Steichen photographs and not works by her mother.

Mr. Bannon said that because the photographs had sat for so long out of the light, their colors remained particularly vivid. “They’re in just as perfect a shape as you could expect from something from almost a century ago,” he said.

Autochromes are positive images, meaning they are unique and not negatives that can be used to create prints. They were made using a complex process in which tiny dyed grains of potato starch were spread across a piece of glass and light was passed through them to a photo-sensitive plate.

The three colors of the starch grains — bright blue-violet, bright orange-red and Kelly green — worked together to produce a wide range of realistic-looking colors, in the same way that combinations of red, blue and green dots produce a color-television picture.

“If you did it right, you had the basic colors you were looking at when you took the picture,” said Mark Osterman, the photographic-process historian at Eastman House.

Unlike most other antique prints, autochromes are usually displayed with a light source behind them, allowing their colors, which are dim in regular light, to shine through the semi-transparent glass or to reflect onto a mirror. But prolonged exposure to light can wash out the images. After Eastman House displays the pictures they will be returned to storage. (The pictures will be exhibited on a light table sometime in October, although a date has not been set.)

Mr. Bannon said it was hard to estimate what the market value of the pictures might have been had Mrs. Albright put them up for auction, but he believed that each probably would have generated six figures. The only other known example of a Steichen portrait like them, perhaps from the same session with Spaulding, is in the collection of the Philadelphia Museum of Art, Mr. Bannon said.

Hans P. Kraus Jr., a Manhattan photo dealer who just mounted an exhibition of antique autochromes by Stieglitz and other Photo-Secession artists, said that Steichen autochromes rarely appeared on the market. The last one he remembered seeing, years ago, was a portrait of J. P. Morgan.

As Mr. Bannon recounted the handoff of the autochromes, he was asked whether he went into the ice-cream parlor for a celebratory cone after he knew exactly what he had in his possession. He said it didn’t even cross his mind.

“With a couple of century-old autochromes in my car, I wasn’t going anywhere but directly back to the museum,” he said. “And I was driving very, very carefully.”