Charles Pratt's photographs, now on exhibition at the Corcoran Gallery of Art, are pastoral and patient. Looking at his landscapes is like sitting in a meadow, in the woods or by the shore, rereading Thoreau.

Pratt (1926-1976) was a kind of Transcendentalist. Unlike other landscape artists, Bierstadt or Moran, or even Ansel Adams, he avoided the dramatic. An Emersonian ethic lends these mild, moral pictures dignity and strength. Pratt preferred nature's quiet to her operatic boomings. He taught himself to see the sublime in the small.

A school of minnows gathers in shallow moving water. A few dead leaves are sprinkled on a grassy forest floor. A gnarled and ancient apple tree, bearing yellow apples, is bathed in pale winter sunlight. A cow reclines in grass. Slim twigs pierce fresh snow. Mist rising in Ireland obliterates the line between gray sea and gray sky.

Thoreau, at home at Walden Pond, spent long afternoons considering such sights. The Hebridean monks who 1,400 years ago decorated the pages of the Book of Kells looked as carefully at the tiny flowers, leaves and vines entangled at their feet. Pratt approached photography with comparable peace.

But the pictures that he left us, both in black-and-white and color, are not at all old-fashioned. Pratt must have looked closely at Jackson Pollock's painted skeins, at Barnett Newman's fields, and at Mark Rothko's colored fogs. He seems to have responded far more to modern painting than to old traditions of the picturesque. That black cow in the grass is a kind of minimalist object. And many of his photographs of snow, of mist, of water, and especially of grasses, are all-over, non-hierarchical field paintings of a sort.

Like Pollock's or Mark Rothko's, they have no horizon. One dripped line by Pollock is no more important than any other, and the same goes for those minnows or those tangled apple branches photographed by Pratt. Many of his photographs, like recent abstract paintings, stress a sort of shallow depth. One looks past waving grasses to the pine cones and the twigs on the forest floor, or past moving ripples to the bottom of the pond. In a number of these pictures one is not quite sure, at first, whether one is looking down or straight ahead.

After leaving Yale in 1948, Pratt spent 12 years in the theater, most as a Broadway stage manager, before becoming a full-time photographer in 1960. Ralph Steiner, in the catalogue, writes that "Charlie was a photographer who had no interest in what was fashionable," but Pratt was well-connected.

He knew his share of masters. He studied, as did Diane Arbus and Washington's John Gossage, with Lisette Modell. "What distinguishes his work, apart from its beauty, is the extraordinary degree to which it is both sensitive and precise," she writes in the catalogue. Robert Frank is just as generous: "Now Charlie's message is beginning to be heard. To me, he gently tells me; I love the light coming up and when it goes down it is not really all gone. There is light coming from somewhere. Charlie's work is like an echo you hear coming from the sky, the water, and the trees."

Gossage and Jane Livingston of the Corcoran together organized Pratt's show. It includes 33 black-and-white and 20 color images, the earliest from 1960, the latest from 1973. Pratt was a meticulously careful printer, and his show is accompanied by a handsomely designed and exceptionally well-printed catalogue. His Corcoran exhibit is elegant and peaceful, and in its own way prayerful. It closes July 11.