Even Nature stood still for Ansel Adams.

Spacious skies, purple mountain majesties, oceans white with foam -- Adams, perhaps the world's most famous photographer, wanted others to see a John Muir wilderness America the way he saw and felt it himself.

"Sometimes," Adams once said, perhaps a bit pompously, "I think I do get to places just when God is ready to have somebody click the shutter." And because he felt wonder and awe at the natural grandeur he saw, he dared to make it more perfect throughout his 68-year career. He was known for his heroic geologic structures and commanding themes; for the precision and skill of his work; and for being an articulate, aggressive champion both of environmental causes and of photography as an art form.

"Ansel Adams: Classic Images," an exhibit of 75 original Adams prints plus some rarely seen large images, mural prints and screens, is currently on view in the ground-floor galleries at the National Gallery of Art. This is only the second show of photography at the gallery; the first was a retrospective of the work of Adams' friend and mentor Alfred Stieglitz.

In the past, curators have concentrated on Adams' monumental images. This exhibition is Adams as he wanted to be remembered, and it functions as a kind of autobiography and retrospective. Here the prolific photographer was his own curator, and the 75 prints in the museum set, selected during the last five years of his life, represent not what he might have called his "best" images, but what he'd been working on his entire life. When he died in April 1984, he had finished printing only six of the full 75-print sets, which he had sold on the understanding that they be kept intact in museums and educational institutions.

Few photographers can hope to approach Adams' household-name status. And indeed the Greatest Hits -- familiar from Sierra Club calendars, greeting cards and the inexpensive reproductions the photographer encouraged -- are all here: "Moonrise, Hernandez, New Mexico" (1941) and "Clearing Winter Storm" (1944), among others. The full range of his work may come as a surprise, but it is still these monumental works that dominate the show.

They are ponderous, planned portraits of nature. Simple empirical representations could not convey the size and distance and emotional power of these vistas. Adams' artistry lies in the process he called "visualization," deciding in advance how the photograph will look, rather than shooting miles of film and hoping one might be usable.

That preconceived image, composed in the camera, was then enhanced and refined with Adams' patient skill and painstaking photographic methods, including his noted Zone System -- a tonal scale of 11 "zones," ranging from total black to pure white, used to determine densities in the finished print.

The museum set includes new prints of some of his earliest work -- including "Lodgepole Pines," the kind of delicate, blurry image accepted as art photography in 1921 -- as well as work from his late period, in which more technical assurance and a bolder, more melodramatic sensibility is evident.

"Sand Dunes, Sunrise, Death Valley, California" (1948) is an exercise in serpentine line and one of the best examples of Adams' mastery of tonal values, shifting from rich blacks to sunbleached sand white. "Surf Sequence 1-5" (1940), looking directly down on the changing ocean from a cliff, recalls Stieglitz's famous "Equivalents" series of cloud photographs, which were intended to represent emotional states.

Adams chose unusual sites -- the minimal landscape of "High Country Crags and Moon" (1935), two bleak peaks and the abyss of the night sky; "Grass and Pool" (1935), white grass etching calligraphic symbols on a pond's black-glass surface. He treated the Rio Grande and Snake River not as bodies of water, but as wide ribbons of light snaking through the flatlands.

Some of these images, like "Frozen Lake and Cliffs" (1932), are so otherworldly it seems Adams must have invented them. And in a way, he did. He manipulated his print of "Mount Williamson, The Sierra Nevada, from Manzanar, California" (1944) so that shafts of sun lend an eerie animation to a field of boulders. In "Mount McKinley and Wonder Lake" (1947), the hazy mountains and the razor-sharp lake seem to be hallucinating each other.

In his portraits, he treated his subjects like landscapes. "Georgia O'Keeffe and Orville Cox" captures the grand old lady's severity and sly humor with the Arizona clouds behind her. The "Spanish American Woman" (1937) is as densely textured as the weathered wood behind her. The show also includes a modest, distinctively un-Adams-ish portrait, "Mrs. Gunn on Porch, Independence, California" (1944).

Adams supported himself as a commercial photographer and did impressive journalistic photo essays of the Japanese internment camps and of children in trailer camps. (He treated these studies as art as well, using the formal view camera rather than the 35mm camera usually used for such work.) But Adams was criticized in the '30s -- by Henri Cartier-Bresson, among others -- for not being "socially committed" enough, for taking pictures of rocks while the world of men was falling apart. Fifty years later, Adams' work seems like a form of preservation, as important in its way as the photography Cartier-Bresson preferred.

The National Gallery exhibit also includes several rarely seen large images, mural prints and screens, many loaned by Adams' wife Virginia. Adams treated these enlarged versions of his pictures as a separate problem -- he knew he couldn't just pick a negative and blow it up, because certain parts of the composition are reemphasized in large format.

The National Gallery installation was assembled by curator of American art Nicolai Cikovsky Jr. according to Adams' own precepts. The photographs are widely spaced in three rooms on light-absorbing, nonreflective gray walls, and are lit with high intensity; in Adams' work, even the blacks have detail, which wouldn't be apparent with insufficient light.

Though the work speaks for itself, some details on Adams' life may enhance a visit to the exhibition.

Ansel Adams, who would probably be diagnosed today as a hyperactive child, only completed eighth grade. But he taught himself to play piano at 13, and later trained as a concert pianist, which was where he felt his calling. At 14, according to an oft-told tale nearly too corny to be true, he brought a Kodak Box Brownie camera along on a trip to Yosemite's Inspiration Point with his parents. -- The rest, as they say, is history.

At age 30, after photographer Paul Strand showed him his negatives, Adams gave up the piano for the camera. In his last interview, for ARTnews magazine, Adams remembered the decision. "Some friends said, 'Oh, don't give up music. A camera cannot express the human soul.' The only argument I had for that was that maybe the camera couldn't, but I might try through the camera."

Still, he retained his sense of musical discipline. He often compared the photographic negative to a musical score and the making of a print to a concert performance -- and he used an electric metronome rather than a timer clock when printing.

Adams was always concerned with helping photography establish itself as a fine art, having chosen his career at a time when books of photography were rare, galleries dealing in photographic prints were rarer, and art museums were (as they arguably still are) uncertain about exhibiting photographic art. He founded (with Beaumont Newhall and David McAlpin) the department of photography at the Museum of Modern Art, and Friends of Photography, the largest such group in the world, with 16,000 active members.

He began his involvement with the Sierra Club in 1919, when, as the club's 17-year-old custodian, he would sweep up and get rid of mice. In 1934, he was elected to the board of trustees, and served to 1971. (Virginia Adams was elected two years earlier, the first woman elected to the board.) His meetings with presidents on environmental issues were well publicized, as were his tangles with James Watt and Ronald Reagan. After his death in April 1984, the National Park Service named a Yosemite peak for him.

The National Gallery show coincides with the release of Adams' autobiography, a 400-page volume he wrote with the help of Mary Street Alinder. The set of photographs on display belongs to the Pacific Telesis Group, a California telecommunications company, which also funded the exhibition.