It will surprise no one that voyeurism, as a path to knowledge (and pleasure, thrills, remorse), and its staring partner, surveillance, have been loosed upon the world. Or that photography and its derivatives have had major roles in placing them smack in life’s center. (Whether we die knowing something because we stare is debatable.) "Exposed: Voyeurism, Surveillance, and the Camera since 1870," a show conceived by San Francisco Museum of Modern Art senior curator of photography Sandra S. Phillips and co-curated with Tate curator of photography Simon Baker, is at the Tate Modern through Oct. 3, 2010, and subsequently opens at SFMOMA on Oct. 30, 2010, and the Walker Art Center in Minneapolis on May 21, 2011.

The exhibition, and its accompanying catalogue, trace the course of the camera’s contribution to the voyeurism of sexual scenes, people caught unaware, street photography, celebrity watching, and the allure of violence -- as well as the surveillance stare, generally unseen by the surveyed and currently ubiquitous.

This tall order has resulted in an enormous show, rather too big for its own good and missing a few important items -- thank goodness, it might have been bigger still -- but full of arresting images and a cornucopia of food for thought.

One early photographic voyeur was an amateur photographer named Horace Engle, who, equipped with a hidden camera, took pictures of unsuspecting passengers on a streetcar back in 1888. (From early in the 19th century, horse-drawn streetcars were one aspect of the urbanization and industrialization that threw people into unusually close quarters, making a degree of voyeurism practically unavoidable. Riders "spied" on people they did not and would not ever know, whether on streetcars or crowded streets, and stared at displays in the windows of photographic studios and lingerie shops.)

The spread of so-called detective cameras in the 1880s -- they could be disguised as a parcel, a stack of books, even a pistol (which might not have been quite so unnoticed), or hidden in a shoe, a hat or beneath a vest -- prompted public unease about being recorded unaware. A photographer caught Degas fastening his fly as he emerged from a pissoir. The first right-to-privacy laws in America, at the beginning of the 20th century, were initiated by the case of a photograph of a young woman that was taken without her knowledge and used in an advertisement that caused her great distress.

Soon there were cameras with a false lens on the front and an actual one on the side, pointing off at a right angle. Paul Strand used such a lens in 1916 when photographing poor immigrants on the Bowery up close. Ben Shahn used a right-angle lens in the 1930s and lent one to Walker Evans, who used it on two occasions. Helen Levitt used one in Harlem.

Photography gratified lust from the beginning. The catalogue notes that the French government prohibited the sale of pornographic daguerreotypes ten years after Daguerre’s process was made public." Photographers making nude photographs tried to circumvent the law by calling them "academies" -- studies for artists. One undeniably pornographic photograph in the show, by Auguste Belloc ca. 1860, pictures a reclining woman, fully dressed, with her skirt pulled back to present her privates to us. (She wasn’t wearing panties, but European women were only beginning to do so at the time.)

The woman caters to the male sexual gaze and covers her face, possibly saving herself from arrest, but leaves one eye uncovered, looking at the looker, thereby turning the table on the voyeur. Similarly, when Robert Frank took a picture of three male hustlers in 1955, two of them gave him come-on looks but the third put a hand over his face, leaving both eyes staring at the photographer from between his fingers.

Technological progress in photographic image making has inexorably expanded the reach of images, voyeurism and surveillance. Cinema almost immediately widened the audience and the sense of intimacy. In 1896, an early projected film by Edison had a close-up of a couple kissing in a Broadway play; as Paul Starr reports in his The Creation of the Media (2004), one newspaper said of this history-making image that "the real kiss is a revelation," but another said it was "absolutely disgusting. . . no more than a lyric of the Stock Yards." One man’s delectation, then as now, was another’s urgent call for censorship.

Defining voyeurism is not as easy as it seems. Sandra Phillips writes about Mapplethorpe that his work "is not really voyeuristic (as he himself correctly observed) because it is highly formal and seeks to redefine beauty by including pornography." Are we to think that Modigliani’s nudes, or even Picasso’s of Marie-Thérèse, aren’t voyeuristic because they are formally composed, or that Lisa Yuskavage’s are not because of their references to soft porn?

Mapplethorpe’s photographs may not be pornographic -- art experts convinced a jury in Ohio that they were art instead -- but it’s disingenuous to claim they are not voyeuristic.  At the Whitney Museum’s Mapplethorpe retrospective in 1988, I chanced upon a docent lecturing before an image of cunnilingus. She discoursed on its formal attributes without once mentioning what it was about. Content counts, in more photographs than this one.

The decorous dictionarians of the OED partially define "voyeur" as "a person who observes. . . without participation, a powerless or passive spectator"-- which might buttress the argument that photography is intrinsically voyeuristic. Certainly Kohei Yoshiyuki’s pictures of people who go to a park at night to watch couples coupling are multiply voyeuristic, implicating the watchers, the photographer -- and us. A photographer contemplating a nude or any sexual subject is also a voyeur, but someone with a camera, or the means to distribute a photograph, is not entirely passive or powerless. (Ask Paris Hilton’s former boyfriend, if you don’t believe me.) Watching violence is sufficiently voyeuristic to dub violence the new obscenity.

Celebrity watching arrived in the mid-19th century with the invention of the carte de visite, a small, inexpensive photograph that started a craze for images of rulers, politicians, cultural heroes et al.,and provided vicarious thrills to those who couldn’t get near the king or a longed-for actress. By the 1950s, Italian paparazzi had turned celebrities into prey, as photographs of Anita Ekberg’s husband chasing the photographer Tazio Secchiaroli with clenched fists make clear.

More recently, rapacious photographers have shared the blame for the Princess Diana’s death. Public figures today largely forfeit their rights to privacy-- admittedly, some are delighted to do so -- and ordinary people do too whenever they stray into public areas. Philip-Lorca diCorcia was taken to court by a man offended by a photograph of him made on the street by remote control without his knowledge; in 2006, the court ruled in diCorcia’s favor.

Photography has exponentially multiplied the age-old fascination with violence, which is evidently insatiable. With so much actual violence in the news every day, it is puzzling that there should be such widespread addiction to the staged variety in film, TV, the Internet, print and games -- it’s not teenage boys alone. Staged violence offers a certain solace: the actors will be resurrected to play in another movie, the avatars recreated in the next game. There is also the kind of thrill that everyday life does not afford and that millions of us now seem to find essential or believe we are entitled to.        

"Exposed" foregoes the staged variety of violence that photographers such as Jeff Wall, Cindy Sherman, Mac Adams, even Les Krims in his parody "Stack O’Wheat Murders" have produced as annotations to our ferocious atmosphere. Instead it proffers documents of grim events like the execution by electric chair of Ruth Snyder in 1928, a gruesome lynching, or Malcolm Browne’s photograph of a monk immolating himself in Vietnam.

The show’s "Surveillance" section includes such documents as police surveillance photographs and FBI spy photographs, but they are far outnumbered by photographic commentaries on the multi-eyed cameras that are now part of our lives and for the most part blithely accepted. In Following Piece, Vito Acconci adopted a basically aimless detective’s mode, following a different pedestrian every day for a month until he or she entered a building. Sophie Calle more intrusively photographed people’s personal possessions when they were out of their hotel rooms, to which she had gained access by taking a job in the hotel as a maid. 

The irony inherent in "Exposed" is that the exhibition is itself an invitation to both voyeurism and surveillance. While you are staring at all those sexy and violent pictures, the museum’s surveillance cameras, which serve to protect its collections, are staring at you. Consider the case closed.

"Exposed: Voyeurism, Surveillance and the Camera since 1870" premiered at Tate Modern, May 28-Oct. 3, 2010; it subsequently appears at the San Francisco Museum of Modern Art, Oct. 30, 2010-Apr. 17, 2011, and the Walker Art Center, May 21-Sept. 18, 2011.

VICKI GOLDBERG is author of The Power of Photography: How Photographs Changed Our Lives, and editor of the anthology Photography in Print.