It's not art until someone sees it

German photographer Thomas Struth started his career not as an artist, but as an art teacher.

In his retrospective "Thomas Struth," at the Metropolitan Museum of Art through May 18, he teaches us how to view the world through active, not passive, perception.

The theme is made explicit on first entering the museum, where gigantic video portraits, 14 feet high and 24 feet across, of Struth's friends are projected on walls of the Great Hall. Staring straight at the viewer, the subjects make explicit the act of looking.

"Struth's concept," according to co- curator Douglas Eklund, "is that the viewer completes the meaning of a work" by participating in creating its meaning.

Seventy photographs, many mural-sized, demonstrate why Struth is a major figure in contemporary art.

As a pupil of German photographers Bernd and Hilla Becker, Struth trained in Düsseldorf, where he still lives. Along with other Becker disciples, like Andreas Gursky and Thomas Ruff, Struth brought the large-scale color photograph from a marginal position in 1970s art to the forefront of contemporary art.

Not content to shape today's art, Struth has made reviving art history a personal crusade. His signature images are scenes of art pilgrims visiting museums and cultural sites all over the world.

His "aim is to unleash the power of paintings," Eklund says. Struth believes "art can transcend all of history's cataclysms," Eklund continues. But past masterpieces must not be considered "fetish objects you kneel down before."

Instead, they are works to grapple with now. "There's a restorative aspect to [Struth's] work," Eklund says. "His pictures are about rehabilitating or cleansing our vision."

A shot of the interior of San Zaccaria Church in Venice shows walls covered with Biblical frescoes by Bellini. The painted figures look just as alive as the tourists studying them. The photo's large scale reveals details with pristine clarity and gives a sense of cohabiting in the space.

His image of Notre Dame Cathedral in Paris gives viewers a "you are there" immediacy. Carved stone prophets and apostles ascend the facade, as lines of tourists stream into the church. Past and present, sacred and secular, merge and diverge.

His famous photograph of visitors observing Caillebotte's "Paris, Rainy Day" in the Art Institute of Chicago (where the exhibition makes a final stop in June) illustrates the interchange between viewer and viewed. The strolling figures in the painting gaze at each other, while visitors to the Art Institute gaze at them. We, in turn, look at the photograph of them gazing.

Space is doubled, then tripled, as views and interpretations multiply. Struth says in the exhibition catalog that his work is about "the contemplation of art as a self-reflection," where the viewer's imagination is activated by the painter's imagination.

The works are displayed in a jumble of genres from various places and times, dating from 1977 to 2002. Struth designed the placement to mix and match different subjects, conveying a sense of connection through comparison and contrast.

His early works are urban streetscapes, devoid of life. "I'm interested in photographs that have no personal signature," Struth said in 1978. The camera records from an anonymous perspective - without narrative anecdote.

The idea, according to Struth, was to allow "enough space and enough silence to just work with yourself."

The photographer stays neutral; the viewer interprets the scene. The composition records the geometry of buildings and varied layers of history. The architecture embodies social, cultural, and economic values. It's all there, but - like an archaeologist - you have to dig it out.

Struth also records portraits of families, facing the camera with deadpan intensity. It's up to the viewer to decipher their invisible ties. A photo of the painter Gerhard Richter's family (Richter was Struth's painting teacher) is as detailed and replete with visual information as Velázquez's "Las Meninas," another tour de force in grays and blacks, with layered relationships to decode.

The photos that most reveal Struth's beliefs in both autonomy and interdependence are from his "Paradise" series.

These scenes of jungles throughout the world originated after the fall of the Berlin Wall, when, as Eklund says, "the split people lived with of two competing ideologies was gone." Struth asked himself, "What do we have left" to believe in?

Eklund compares the gallery of grandly scaled photographs of dense foliage to "the Rothko Chapel, with its marvelous, spiritual quality." The eye gets tangled up in green, as one takes in lushly intertwined trees, vines, and leaves dappled with sunlight, each distinct, yet organically connected.

Photography, Struth says, "is a communicative and analytical medium."

What the images communicate depends on the viewer's analysis. Struth refrains from imposing his own vision, but his selection and composition of images convey voices singing solos and in unison.