The Georgia O'Keeffe exhibit at the Phillips Collection isn't the only tribute to O'Keeffe's vision that's now showing in Washington.

The National Gallery East Building is featuring "Photographs From the Collection," an exhibition of 65 rare images, many of them exquisite, that were recently added to the gallery's 50-year-old photography collection. O'Keeffe launched that collection in 1949 when she donated 1,600 prints by her recently deceased husband, the great Alfred Stieglitz, to the unproven eight-year-old institution.

But for that gift, the gallery might be without a photo collection: It remained uninterested in the subject for the next 40 years.

"It was amazing that O'Keeffe gave it, even though she knew the gallery might not do much with photography for a while," says Sarah Greenough, the gallery's curator of photographs. It wasn't until 1989 that the gallery established a department of photographs, appointed Greenough to head it and, under pressure from an art world smitten with photography, finally began building upon O'Keeffe's priceless legacy.

Since then, the collection has swelled to 2,500 images--still small compared with older and richer collections in New York, Chicago and even here in Washington at the Library of Congress, the National Archives and the Smithsonian. But as this show makes clear, it is a trove that seems on the verge of bursting into bloom.

The point is to illustrate, through the finest examples, how the collection has expanded--both geographically and chronologically--since the acquisition of 150 photographs from the Mary and David Robinson Collection in 1995. Rich in rare and beautiful images by pioneering 19th-century photographers in France, England and America, the Robinson collection broadened the scope of the gallery's 20th-century American holdings to embrace the entire photographic era, from its beginnings in 1839 to the present.

Since then, several other early images have been added, most remarkably three salted paper prints by the pioneer English photographer William Henry Fox Talbot, who--only four years after photography was invented--captured forever the look of a Paris boulevard with its stately buildings and bustling horse-drawn coaches. Work by other pioneers, such as Eugene Atget, Gustave Le Gray, Julia Margaret Cameron and Nadar, are also represented, the last by an affectionate portrait of the French painter and caricaturist Honore Daumier.

The quality of the Robinson acquisition is clear from the start. Two mesmerizing 1867 landscape views of "Cape Horn, Columbia River, Oregon," by American photographer Carleton Watkins, project a mood of almost lunar tranquillity. Time has also stopped in several photographs by Atget, including his elegiac turn-of-the-century view of "Corot's Pond, Ville-d'Avray." More recently acquired, but related in its nature-worshiping spirit, is a photograph by the American John Moran showing an artist (probably his brother Thomas) sketching, perched on a large rock in the middle of a peaceful, tree-shaded river, "The Wissahickon Creek Near Philadelphia."

Throughout the show, Greenough has grouped related photographs to amplify meaning--portraits, moonlit landscapes, couples, modernist experiments. An 1856 female nude by a recently rediscovered French photographer named Franc Chauvassaignes, for instance, is shown alongside two monumental 1916 Stieglitz photographs from his "collective portrait" of his future wife, a resplendently nude O'Keeffe. Though they are a half-century apart, all are similarly defined by light.

Paris and New York in the '20s and '30s provide an especially rich source of inspiration illustrating the wide range of feelings different photographers can wrest from the same subject. Like countless other artists, Hungarian photographers Brassai and Andre Kertesz and Berliner Ilse Bing made their way to the City of Light during those years and reveled in its pleasures, creating bold and often fabulous photographs. Kertesz, especially, is revealed here to be an artist of tremendous emotional range, first delighting in the play of shadows on the ground beneath the Eiffel Tower, and later, in New York, sensing something ominous and disorienting in a view of a skywriting airplane, writing backward and upside down over a looming Rockefeller Center.

And then there's Berenice Abbott, who hymns the looming verticality of New York's skyscrapers, which she defines with slivers of light. And Stieglitz, the photographer-art dealer, who looks out the window of his last gallery, An American Place, and senses melancholy isolation.

Of the most recent photographs on view, the most unforgettable is Roy DeCarava's masterpiece "Car Behind Building," a haunting scene in which a '50s Buick appears from behind a building in a deserted Manhattan street and is transformed into an ominous, anthropomorphic presence.

The groupings also serve to underscore a central point: "The most gifted photographers do not simply record their world but transform it, endowing it with meaning and significance," Greenough says. "We're not trying to represent the work of all photographers in the history of time, but rather those who have used the medium as a form of artistic expression."

This emphasis on the power and meaning of photographs, rather than their historical value, is refreshing and admirable. "We're seeking to acquire major masterpieces by the most important figures in the history of photography, but hope we can see them in a fresh way, and not just through the images that textbooks have endlessly reproduced," she says.

Freshness is indeed the hallmark of her show, which makes it a worthy tribute to her discerning eye, as well as to the generosity of the photographers, photographers' survivors, foundations and low-profile donors and collectors who've supported the collection and helped it grow. Happily, one such patron and teacher--the late, great photography dealer Harry Lunn--is honored here by the presence of a splendid full-length photograph of Stieglitz, taken by Heinrich Kuhn in 1907. A favorite of Lunn's, it hung for years in his Washington home and later in his Paris apartment. It was recently presented, in his memory, to the gallery by his friends and family.

There's an amusing footnote to the story of the collection's birth, told years later by O'Keeffe herself. She said that this "key set" of Stieglitz photographs was originally destined for the Metropolitan Museum in New York, but that she had changed her mind when a Met curator told her the mats surrounding them would have to be cut down to fit standard storage boxes. O'Keeffe explained that the mats were a very important aesthetic consideration for Stieglitz and that he didn't consider the work complete without them.

"We do it with all our fine prints and drawings, including our Rembrandts," explained the curator.

"Well Mrs. Rembrandt wasn't around to complain, and I am," replied O'Keeffe.

And so the photographs came here.

"Photographs From the Collection," at the National Gallery East Building, Fourth Street and Constitution Avenue NW, through July 5. Hours: Monday-Saturday, 10 a.m.-5 p.m.; Sunday, 11 a.m.-6 p.m. Admission is free.

CAPTION: Among the old and exquisite images in the "Photographs From the Collection" exhibit are William Henry Fox Talbot's 1843 "Orleans Cathedral," left, and Andre Kertesz's "Clock of the Academie Francaise, Paris," from 1929-32.