Our Porn Stars, Ourselves. “This exhibition contains explicit images,” reads the placard at the entrance of “Larry Sultan: The Valley,” “SFMOMA recommends that adults preview the exhibition before sharing it with children.” At first, it’s hard to tell what they’re talking about. The first image in the gallery is called “Backyard Film Set,” and includes a lush lawn, a rather innocuous trash can and an elm tree bathed in ethereal light. Puzzling, perhaps, but hardly explicit.

Stick with the show, however, and you’ll discover what the placard means. The film in progress on “Film Set” isn’t, say, a suburban family drama. It’s an adult movie, one of many routinely shot in rented tract homes in LA’s San Fernando Valley. These homes form the setting for Sultan’s latest project. His human subjects are those deities of American popular mythology, porn stars.

Sultan understands this mythology, characterizing the actors he met as the sexual icons of American high schools. “We all remember those,” he says, “who found ways of using their bodies to get what they needed.”

But “The Valley” doesn’t indulge our adolescent fantasies.

Says Sultan, “I’m not interested in the come shot.”

The kinds of shots he is interested in are the ones that reveal not fluids, but psyches. The San Fernando Valley, where Sultan grew up, isn’t just the capital of our country’s porn industry. It’s also a classic example of American suburbia, and the intersection of these two worlds is what motivates Sultan’s work.

In “Den, Santa Clarita,” a naked posterior juts out into what is otherwise a normal living room, complete with home entertainment system. “West Valley Studio #3” features a lush-haired, partly naked actress — and an exercise bike. And in “Child’s Bedroom,” the titular room contains a shelf of dolls, some family photographs and, reflected in the mirror, the lush blond hair of someone decidedly not a child.

Despite their differences (after all, a porn film may be the opposite of a family film), Sultan’s work explores a connection between pornography and family life. In many of his tract-home settings, it seems that one family has moved out, only to be replaced by a new one — stranger, perhaps, but no less close.

“Tasha’s Third Film” shows a woman in curlers reclining on a couch. Flanking her are two men sleeping like babies — the effect is one of people totally comfortable with one another. In “Patio, Delita Drive,” two women sit on deck chairs, both naked but partially covered. Physically, they are as similar as sisters, and their calm, slightly amused expressions suggest Sultan has interrupted an intimate conversation.

“Intimate,” in fact, is a word Sultan uses to characterize the sets he visited. And it’s not a euphemism for him. He describes the cast and crew of a porn film as united by surprisingly close relationships, likening them to “a circus family.”

Given the exhibition’s subject matter, the comparison seems fitting. Adjusting each other’s costumes, relaxing together on a patio or couch, the people in “The Valley” often display a heartwarming tenderness. But Sultan never lets us forget that these subjects are performers, that even in their most private moments the show is going on.

Sometimes this show is obvious. Sex acts are visible in many of the images — a masked man enters a woman from behind, a threesome takes place beside a pool, a quiet living room scene gets a dose of oddness from a knot of writhing forms outside.

But not all the photographs contain naked bodies. In those more suitable for children, the eroticism comes through in Sultan’s skill with color and light. Lawns are emerald green. The red upholstery of a couch takes on the depth and luster of apple skin. And more often than not, light appears to come directly from Heaven.

Pornography, for Sultan, isn’t just an aid to adolescent masturbation. It’s also the expression of our collective fantasies, a way of “compensating for the isolation of the suburbs.” It’s not just the actors who are on display here, but the Valley itself, and, as Sultan’s photographs reveal, it becomes a kind of Eden.

This Edenic quality is perhaps most obvious — and problematic — in “Woodland Hills Backyard.” Shot in slanting afternoon light, the yard is a vision of green turf and pink flowers. A woman in a black bikini faces the setting sun, which bathes her in a golden glow.

The foreground of the photograph, though, shows a man and a woman, seated far apart, directing at each other sidelong glances that suggest mistrust. The woman in the bikini may be a figure of fantasy, but this couple seems decidedly Earthly. If they are Adam and Eve, this is after the Fall.

Despite its closeness, the porn family is not exactly a happy one. As performance, pornography is grueling — Sultan is careful to note the enormous physical stress porn actors suffer in their work. That this stress has recently exploded into outright danger comes as no surprise to him at all.

Asked to comment on the recent rash of HIV infections among the Valley’s porn actors — five cases have been confirmed in the past month, four linked to a single infected star — Sultan described the problem as “unfortunate,” but “not shocking.” While performers were required to produce records of STD tests before each shoot, these records were not foolproof. Sultan’s suburban paradises take on a different character when we insert into them the ever-present threat of disease.

Beautiful bodies embracing in heavenly light may glamorize suburban life. However, they also reveal suburban appetites whose satiation sometimes comes at terrible cost. In the end, porn actors take risks no family can protect them from. They are not guests in the Valley’s tract houses, making themselves at home while the residents are away. Rather, they are there to service these residents’ desires.

The most disturbing image in “The Valley” is called “Little Cinderella.” Its subject is a waiflike blond woman lost in a gray sweatshirt, standing on a rundown Valley street. Gone are the support system of costars and crew. Gone are the beautiful saturated colors. “Cinderella” is alone in an unfriendly, unlovely world.

If we see “Cinderella” as a porn actress, her image exemplifies the pain of her profession. Marginalized like circus performers, women like her satisfy the cravings of others at the cost of their own safety. If, on the other hand, she’s an ordinary suburban woman, she might embody the reason for these cravings.

Nowhere is “the isolation of the suburbs” more apparent than in the eyes of “Little Cinderella.” Nowhere is the need for a fantasy of rich color and reckless coupling more obvious than in the drainage ditches and empty yards of the street behind her.

Larry Sultan spends much of “The Valley” examining how pornography creates the illusion of a suburban Eden. But the most powerful of his images may be the least Eden-like. Only when he strips away the illusion do we see why we might so desperately desire it.