Year after year thousands of photographers attempt to capture the scenic grandeur of our national parks. But the most exceptional photographs of the American landscape are the work of one man: Ansel Adams.

Before digital photography, before memory cards capable of holding thousands of pictures, there was Adams and his 8x10 view camera, getting one or two shots of his subject and somehow besting all of the competition.

When "Ansel Adams: Celebration of Genius," the largest show of his work ever mounted by George Eastman House, opens on May 12, viewers can see 150 of Adams' greatest photographs. Some of them are iconic scenes like "Moonrise, Hernandez, New Mexico." Others are rarely seen treasures.

The traveling show, which has been breaking records at every venue from Spain to Florida, will end its tour next year in Scotland. It is expected to be one of the most popular shows ever at Eastman House. (See box for special hours and prices.)

If 150 photographs sounds like a lot, consider that the Eastman House actually houses 270 of the master's works.

"It's one of the treasures of our collection," says Jeanne Verhulst, associate curator of exhibitions and curator of the show.

Adams had a special relationship with the Eastman House that can be traced back to his fondness for the museum's first curator, Beaumont Newhall, and his wife, Nancy, a writer who collaborated with Adams on several books.

He visited the Newhalls several times at their home on Rundel Park and even house-sat for them while they traveled in Europe. But Adams' impressions of Rochester were less than enthusiastic:

"I found the town itself dismal, with a climate that was difficult to say the least," he wrote in his autobiography, published a year after his death in 1984. "I cannot imagine anyone willfully living there. The chief urban voices of Rochester are the police and fire sirens, practicing their wailings at all hours of night and day. San Francisco has its foghorns, Rochester its sirens."

Adams knew those foghorns well. In 1902 he was born Ansel Easton Adams to a well-to-do family that lived on the shore of the (pre-bridge) Golden Gate of the San Francisco Bay. Named after his uncle Ansel Easton, he dropped his middle name from his signature after his namesake undermined his father in a business deal.

According to his autobiography, Adams was far from a model child. In fact, bored by what he considered to be useless memorization, he had an outburst in class that got him kicked out of school before his 12th birthday. At home, he was prone to asking impertinent questions about sex and God. He eventually took a test that gave him the equivalent of graduation from the 8th grade.

His father had other ideas about education and bought him a year-long pass to the Panama Pacific Exposition, exploring the building of the Panama Canal. Around that time the family also purchased a piano and Adams took to it immediately. Later, he would write that the discipline he learned practicing the piano served him well in terms of patience and quality in his photographic work.

In a strange way, Adams was introduced to photography from inside the camera.

Soon after leaving school, he was bedridden for two weeks with the measles. Looking up at the ceiling in his darkened room, he noticed an upside-down, blurred version of the world outside. As it turned out, small holes between the shade and window were creating "pinholes" that converted his room into a camera obscura. When his father opened a Kodak Bullseye camera to explain the phenomenon to him, he was fascinated.

"Ansel Adams, An Autobiography" (with Mary Street Alinder) goes on to recount other pivotal events in his life.

Bedridden again in 1915, Adams was given a book to read: "In The Heart of the Sierras" by J.M. Hutchings.

So taken was he with the descriptions of Yosemite, he talked his family out of their vacation plans and into a trip to the national park. On the morning after their arrival, he received the gift that would change his life: his first camera, a Kodak Box Brownie.

His first try at nature photography was inauspicious. He balanced himself on a tree stump to get a better angle on the rock formation known as Half Dome. The rotted stump crumbled and Adams fell as he snapped the shutter. The result was an upside-down image of Half Dome - but it wasn't a bad photo.

It was while taking another picture of Half Dome ("Monolith, The Face of Half Dome") in 1927 that Adams first used the technique that would set him apart from the crowd. He called it "visualization."

"I began to think about how the print would appear and if it would transmit any of the feeling of the monumental shape before me in terms of its expressive-emotional quality," he wrote in his autobiography. "I began to see in my mind's eye the finished print I desired: the brooding cliff with a dark sky and the sharp rendition of distant, snowy Tenaya Peak."

Adams didn't just snap the shutter and accept the result. He made the technical adjustments (through a particular angle, filter and exposure) that would capture the scene  in as dramatic a way as he reacted to it.

He eventually got so adept at visualization, he was able to make aesthetic decisions in split seconds. His most famous photograph, "Moonrise, Hernandez, New Mexico," is a case in point.

Adams was traveling with his 8-year-old son Michael and a friend, violinist Cedric Wright in 1941, when he noticed the wondrous scene.

"I steered the station wagon into the deep shoulder along the road and jumped out, scrambling to get my equipment together, yelling at Michael and Cedric to ‘Get this! Get that, for God's sake! We don't have much time,'" wrote Adams.

But once the camera was in place and the image composed, he couldn't locate his exposure meter. And the sun was about to disappear.

"He wasn't going to take a 35mm shot, which certainly would have been available at that time," says Verhulst. "He wanted his 8x10 camera and took the time to set that up. He knew what the luminance of the moon was and guessed at the exposure. By the time he flipped his film over to take a second shot the light was gone, the sun had set."

With just one shot Adams had managed to create one of the greatest landscape photographs ever taken.

Of course, taking the photograph is just the beginning.

"Adams spent hours and hours in the darkroom creating an image that he felt best represented his vision when he was standing before that scene," says Verhulst.

Today many photographers will make adjustments and enhancements to their digital images in computer programs like Photoshop. For Adams it was literally a hands-on process.

Although "burning and dodging" is a technique still used by traditional photographers, their number is shrinking.

Verhulst describes the process Adams used: "You project the negative onto photographic paper. Trial and error tells you where you might have to add light (burning) or withhold light (dodging) from certain areas. Normal tools are handmade implements. A burning tool might be a thick piece of paper with a hole in it to allow light to penetrate through to a small area. A dodging tool might be a wand with various sizes of paper or cardboard held with both hands to add and subtract light for varying amounts of time."

As for continuity of printing from one photograph to another: "People make maps of when (in seconds) and where they dodged and burned during an exposure," Verhulst says. "Adams and his assistants would follow that map."

One technique Adams developed tied the shooting and printing of photographs together in the mind of the photographer. He codified it in 1940 while teaching at the Art Center School in Los Angeles.

Called the Zone System, it was, according to Adams in his autobiography, "a framework for understanding exposures and development, and visualizing their effect in advance."

He did this by breaking up the composition (or scene) into zones from black to white with shades of gray in between.

"Areas of different luminance in the subject are each related to exposure zones and these in turn to approximate values of gray in the final print," Adams wrote.

By all accounts, Adams was gifted enough to have had a career in music. His decision to pursue photography was sealed when he met Paul Strand in Taos in 1929.

"In this little artist colony, Strand showed him his prints and negatives," says Verhulst, "and his enthusiasm persuaded Ansel that there was a life in photography."

But at the time when most of the show's pictures were taken photography was hardly the respected fine art medium it is today. Throughout much of his career, Adams needed to take on commercial work to survive financially.

He shot grammar school class photographs and wedding pictures, proving that he was more skilled at shooting with natural light in those pre-flashbulb times. In his autobiography, he confesses to setting off smoke-filled explosions by miscalculating the amount of flash powder he used.

He photographed factories, loaves of raisin bread, and shot several of the gigantic (18-feet-high, 60-feet-long) Colorama photographs for Eastman Kodak Co's display at New York City's Grand Central Station.

The struggle to raise photography to the status of fine art was being pursued by many photographers during the first half of the 20th century. Among them were the pictorialists, known for purposely shooting hazy shots and creating photographs that resembled paintings.

But Adams had a different philosophy. In reaction to the pictorialists (who Adams and his colleagues called the "fuzzy-wuzzies") he joined Imogen Cunningham, Edward Weston, and others on the west coast, in forming Group f/64 in 1932. In contrast to the pictorialists the members of Group f/64 saw beauty in seeing things clearly. According to Adams' autobiography, they believed in "photographs that looked like photographs, not some other art form."

On the east coast Alfred Stieglitz was at the center of pictorialist photography. Although Adams found Stieglitz to be cold, rude, and snobbish on their first encounter, they soon became friends, partaking in discussions about Stieglitz' notion of "equivalents," or metaphorical photographs dealing with subjects like cloud formations.

In the end the pictorialists and Adams had a lot in common.

"They wanted to be treated as artists, not documentarians of the landscape, and that evidently was a pretty hard sell through the years," says Verhulst. "Adams had to fight for credibility."

Looking at photographs like "Thundercloud From Glacier Point, Yosemite Valley, California" it is obvious that Adams found his sense of the spiritual in nature. He rejected organized religion but loved Henry David Thoreau and his philosophy.

Adams was active in the Sierra Club and spent 37 years on its board. He led countless trips into the mountains and felt very strongly about conservation before it was a popular issue.

While almost all of Adams' most striking landscapes of Yosemite and other places will be on display, Verhulst hopes visitors will move beyond the familiar.

"When I started looking at some of the less known images, they were just as interesting to me," says Verhulst.

For instance, "Detail, Picket Fence," a picture of six vertical planks and a cross beam in the sunlight, is not a well-known photograph, but she believes it is among the most fascinating.

"He takes this picture of a fence that, to me, replicates these mountains. It comes close to ‘Monolith,'" she says.

The show also includes portraits of photo giants Weston and Stieglitz, Polaroid inventor Dr. Edwin H. Land, artist John Marin, and others.

And, although Adams did not like the word "abstraction" applied to his photographs, the exhibition contains images like "Roots, Foster Gardens, Honolulu, T.H.," that read beautifully as abstractions.

Even a realistic image, like "Moon and Half Dome, Yosemite National Park," is so beautifully composed in terms of positive and negative shapes that it is a magnificent example of balance in abstract composition. And that perhaps is the strength of Adams' oeuvre; he recreated the landscape with a heightened sense of drama, making already glorious scenes transcendent.

"Ansel Adams: Celebration of Genius" opens Saturday, May 12, and continues through September 3 at George Eastman House, 900 East Avenue. Hours are Tuesday-Saturday, 10 a.m.-5 p.m.; Thursday 10 a.m.-8 p.m.; Sunday 1-5 p.m. During the month of May, hours are daily 10 a.m.-5 p.m., and until 8 p.m. on Thursday. The show will also be open on Memorial Day and Labor Day holidays. Tickets: $12 adults, $10 seniors (age 60 +), $8 students, $3 children 5-12, free, 4 and under. Members free.

For information on a variety of programs, including an August 12 lecture by Michael Adams titled "Ansel Adams: A Son's Perspective," visit: www.eastmanhouse.org