Moon and Half Dome, Yosemite National Park, 1960

He was fifty-eight, and he had been photographing this valley for forty-four years — since 1916, when a fourteen-year-old with a Kodak box camera talked his parents into a Yosemite vacation. He married Virginia Best, whose father kept the painter’s studio below Sentinel Rock; her gallery, Best’s Studio, would sell his prints to park visitors for the rest of the century. He had served on the Sierra Club’s board since 1934, and that same year, 1960, the club published This Is the American Earth — his book with Nancy Newhall that became a founding text of the modern conservation movement.

The tool of his late career had come as a gift: Victor Hasselblad sent Adams one of his cameras in 1950, and the two men corresponded for years as Adams tested and helped refine it. “New seeing with Hasselblad!” he wired the Newhalls. By 1960 the square-format camera rode with him everywhere — which is why, when the moon appeared beside Half Dome, the picture could be made from the trunk of a car.

“I was driving a bit aimlessly around the valley,” Adams remembered, “when I clearly saw an image in my mind’s eye of Half Dome as the moon rose over its right shoulder. I parked my car and with my Hasselblad and tripod firmly positioned across my shoulder, I strode over the snowy field in front of the Ahwahnee until I found the place that best revealed the scene.” The sky was clear, and late-afternoon shadows were advancing on the 2,000-foot cliff of the Dome.

On the tripod: the Hasselblad 500C, a 250mm Zeiss Sonnar to compress the space between moon and mountain, and a Zeiss orange filter to darken the sky so the moon could “shine with conviction.” To keep the camera still he released the mirror before firing the shutter — the moon moves its own width every two minutes, and at this magnification there was no room for blur.

The proof sheet survives: “twelve exposures, an entire roll” of 120 film, as his biographer counted them. Adams waited “until the moon rose to a favorable position” and exposed at intervals of about a minute — two frames on the wider 150mm Sonnar, “by no means as effective” as the 250 — uncharacteristic patience from a man who called bracketing “nothing but indecision.”

Even the choice of negative moved. Adams’s first pick — marked with his darkroom hole punch — gave way after years of printing to a neighbor on the same roll, the negative that still makes the Special Edition prints today. And the film itself carries a story: Adams remembered Kodak Panatomic-X; Alan Ross, who still prints from this roll, reads its edge markings as Adox R17. Every print is a vertical crop from these squares — “the cropping closely determined from the start” — except his one mural, which keeps the negative nearly square.

The Ahwahneechee called it Tis-sa-ack, for the woman of the legend whose face darkens the cliff. Geologists say the “missing half” was never there: the dome grew as granite cooled deep underground, then shed its face in sheets along the rock’s own joints as glaciers cut the valley below. It was called unclimbable until George Anderson drilled his way up the summit route in 1875. Adams gave it the last word himself: mountaineers had told him “the three most distinctive mountain shapes in the world are the Mustagh Tower in the Karakorams, the Matterhorn in the Alps, and Half Dome in Yosemite.”

Photography and this mountain grew up together. Watkins hauled a mammoth-plate camera into the valley in 1861, and his prints helped persuade Congress to protect Yosemite in 1864 — the first time the United States set aside wild land for its own sake. A century of photographers later, Adams answered the same face twice: Monolith in 1927, close and vertiginous, and this picture in 1960 — the mountain composed, at last, with its moon.

The dating is written on the back. Adams stamped his mounts with the studio credit of the moment, and the sequence of those stamps is scholarship — Karen Haas and Rebecca Senf, of the Museum of Fine Arts, Boston, published the standard chronology. This mount carries stamps 7 and 8, the pair in use from 1963 to 1973 — after his move to Carmel, before the late-seventies stamps of his final printing years. Beside the stamps, a period hand has titled it in ink “Half Dome & Moon” — in those years the picture’s name hadn’t yet settled; the Museum of Fine Arts, Boston holds a 1962 print inked “Moonrise – Half Dome.”