In 1991, when John Szarkowski was preparing to step down from his role as director of the department of photography at the Museum of Modern Art, U.S. News and World Report wrote, “Szarkowski’s thinking, whether Americans know it or not, has become our thinking about photography.”

Mr. Szarkowski “gets it in the broad sense,” Phil Block, the director of education at the International Center of Photography, told me during a recent telephone conversation.The “it,” of course, is photography. The “broad sense” covers Mr. Szarkowski’s career as a photographer, historian of photography, theorist of photography, writer on photography, editor of photography books, curator of photographic exhibitions, teacher of photography at Harvard, Columbia, Williams, Cornell, and his alma mater, the University of Wisconsin, and his enormously productive tenure at MoMA from 1962 to 1991. (He still holds the title of director emeritus.)

We will be hearing a lot about Mr. Szarkowski this month. His exhibition of recent photographs, “Now,” opens today at Pace/MacGill, and a major retrospective of his work, which covers more than half a century, opens at MoMA in two weeks. I will write about his photography at that time, but for now I will examine his reputation as a curator and scholar.

Mr. Szarkowski has a holistic grasp of the photographic medium. He seems always to have everything in mind — history, aesthetics, technology — and to be able to put it in the broad context of all he knows about art in general. Whatever he is doing at any one moment is informed by everything else he has done and knows. He is complex, but, as Mr. Block told me, he affects people “like haiku. It is amazing that a layperson can understand someone so brilliant.”

Mr. Szarkowski (b. 1925) succeeded Edward Steichen, the populist, who had succeeded Beaumont Newhall, the scholar, at MoMA, the first art museum to have a department of photography. The exhibitions he curated often became inflection points in the history of the medium. He bought Berenice Abbott’s collection of Eugene Atget’s work for MoMA because, as Mr. Block explained, “he knew Atget was a key to understanding photography in the new century.”

The exhibition and book Mr. Szarkowski produced established Atget’s place in the canon. He rehabilitated André Kertész’s reputation after he had languished unappreciated for 25 years in America. And he had a preternatural ability to recognize new talent, the most valuable asset a museum director can have. One exhibition alone, “New Documents” (1967), introduced Diane Arbus, Lee Friedlander, and Garry Winogrand to a wider public than they had known.

Perhaps his most prescient find was William Eggleston, whom he exhibited in 1976. Mr. Block reminded me of the controversy that surrounded the Eggleston exhibition: It was described by the New York Times as “the most hated show of the year.” But, Mr. Block said, “It was brilliant for Szarkowski to take this raw talent and see the originality of his work.”The show permanently altered the perception of what color photography could, should, would be.

Amazon.com lists 63 books Mr. Szarkowski wrote, edited, or contributed to. One of the most influential is “Looking at Photographs: 100 Pictures From the Collection of the Museum of Modern Art,” a book based on an exhibition Mr. Szarkowski curated in 1973, and for which he wrote one-page essays on each picture. Mr. Block calls this book a “foundation for teaching” about photography: It has been in print since its first publication more than 30 years ago, and was revised in 1999.

“This is a picture book, and its first purpose is to provide the material for simple delectation,” is Mr. Szarkowski’s opening sentence. Note his “first purpose” is to provide pleasure. He wants us to enjoy these photographs; to help us do that, he tells us about the people who took them, the circumstances under which they were taken, the technical details when they are relevant, and the political or social backgrounds when they are pertinent.

The artists included in “Looking at Photographs” were mostly the great names — Julia Margaret Cameron, Lewis Hine, Edward Weston, Richard Avedon — but there were several attributed to “Photographer unknown,” including two aerial reconnaissance photos from World War I. Mr. Szarkowski wanted to open the spectrum of what could be appreciated: He taught people how to see and how to talk about what they saw.

Mr. Szarkowski’s genius is for simplicity. His description of Winogrand’s picture of a couple in front of a wolf in a cage at the zoo, “Untitled” (c. 1962), could just as well be a description of his own prose style: “Granted that simplicity is a virtue; beyond this it is too complex a matter to generalize with impunity. One might add with reasonable confidence that simple does not mean vacuous, obvious, plain, habitual, easy, formulated, banal, or empty.”

The diction is precise, the syntax straightforward, but by the end of the sentence a lot has been said.There is no jargon,nor any of the inaccessible technical gobbledygook less brilliant people use to sound profound about matters beyond their grasp.

Of “Old Faithful Geyser, Yellowstone, National Park” (1941), Mr. Szarkowski writes: “Ansel Adams attuned himself more precisely than any photographer before him to a visual understanding of the specific quality of the light that fell on a specific place at a specific moment. For Adams the natural landscape is not a fixed and solid sculpture but an insubstantial image, as transient as the light that continually redefines it.This sensibility to the specificity of light was the motive that forced Adams to develop his legendary photographic technique.” Such a sophisticated analysis, so plainspoken.

By the 1980s, Mr. Szarkowski was being attacked by postmodernists, poststructuralists, deconstructionists, Marxists — people with agendas. Mr. Szarkowski’s attention to the “simple delectation” of photography will outlast their meretricious grousing.

When I first called Phil Block at his office, he told me he was too busy to talk, then he went on for an hour as one thought about this extraordinary man led to another; eventually he got control of himself and told me to call back the next day. That’s the hold John Szarkowski has on the affections and imaginations of those who have been fortunate enough to know him personally, and by implication the effect he has had on all who value photography.

“John Szarkowski: Now” at Pace/ MacGill Gallery until February 18 (32 E. 57th Street, ninth floor, between Madison and Park Avenues, 212-759-7999).

“John Szarkowski: Photographs” at MoMA from February 1 until May 15 (11 W. 53rd Street, between Fifth and Sixth Avenues, 212-708-9400).