Looking down from Tate Modern’s first floor balcony you can see the scar left by Doris Salcedo’s 2007 exhibit Shibboleth, a lightning strike of new concrete which runs the length of the vast Turbine Hall. Perched up here you could happily spend a great deal of time watching people coming in from the rain and negotiating the hall’s gentle slope. Though currently empty the room still has the power to elicit a response. Children run and skip when they get through the doors, people sit against walls eating their lunch, and here and there bodies are sprawled on the floor as people stare up at the steel-girder ceiling. This is part of what Tate Modern has brought to London in the ten years since it opened: an inviting public space in which to encounter visual art and the idea that art-appreciation shouldn’t be solely the province of small, intimidating, elitist galleries. As one of 5 million visitors per year you are afforded both the chance to view some spectacular modern art, and the chance to observe other people doing the same.

The latest exhibition to take up residence on Tate Modern’s fourth floor,Exposed: Voyeurism, Surveillance & the Camera, combines these ideas of art and people-watching, and challenges us to reconsider where the boundaries might lie. In five thematic sections through more than a dozen rooms the visitor is presented with images which raise questions of intent, privacy, security and eroticism.

Entering the first room of the exhibition you’re met with enlargements of shots from Philip-Lorca diCorcia’s series Heads. The images were taken from a great distance when pedestrians in New York unwittingly tripped automatic lights diCorcia rigged on the sidewalk. The text accompanying the photos tells you that one of the artist’s subjects took legal action against him, with the court eventually ruling in diCorcia’s favour. By choosing to present this material first it feels as if the exhibition’s curators are tipping their hand in the voyeurism / art debate which plays out over the following rooms. In the rest of the “Unseen Photographer” section we’re shown images taken through buttonhole cameras (neatly presented in circular frames) and one-way mirrors, and introduced to the technology of the “lateral viewfinder,” positioned at a right angle to the camera’s true lens to allow for surreptitious “sideways” photography.

By sequencing “Celebrity & the Public Gaze” as the next section, the curators ask visitors to consider whether the rules are – or should be – different for the famous. The curators have performed a careful balancing act, leaving the question open to our interpretation. On one wall there are several of Ron Galella’s photos of Jackie Kennedy, one (“What makes Jackie Run?”) in which she is actively fleeing the photographer. On an adjoining wall Marilyn Monroe’s dress billows as she poses atop an air vent. The fact of the subjects’ celebrity brings a unique push and pull to the relationship between photographer and photographed and challenges us to separate public and private personae. The vibrant candid shot of Jack Nicholson which dominates one wall shows him swinging a golf club at the car of a driver who had just cut him off. There is a strange “in-character” element to the image and it takes effort to see it as something other than a movie screenshot.

The next two sections are the exhibition’s most challenging, and they form a neat duologue of two big themes: sex & death. It’s not so much the explicit nature of the images within “Voyeurism & Desire” which sets you on edge, as the element of illicitness in their having been taken and now in their being displayed. I felt acutely aware of the people around me through these rooms, and watching others’ efforts to appear to be “appreciating” this “art” in an acceptable manner added an enjoyable meta-level to the exhibition’s central themes. This section also contained some of the most striking images, and two exceptional pieces of hanging: selections from Merry Alpern’s Dirty Windows series, presented in four rows and three columns, evoking a grid of windows in a tower block;and the frankly creepy shots from Kohei Yoshiyuki’s 1971 infrared series The Park individually illuminated by spotlights in a darkened corridor.

“Witnessing Violence” develops another human preoccupation in similarly captivating fashion. In amongst the obligatory stills from the Zapruder film Oliver Lutz has found a way to place the observer within the image. A large black canvas hangs alone on one wall, its image only revealed when viewers looks at a monitor positioned nearby so as to frame them directly in front of the picture. The technique, which involves covering the photograph in infrared sensitive pigment, is perhaps a little gimmicky but nevertheless impactful as another way of making visitors reassess their relationship with the images on display.

The final section, “Surveillance,” is perhaps the weakest. The divide between viewer and subject is increased, the images are often of lesser resolution and there is a detectable lack of human engagement in their making. These are largely pictures taken automatically, or single frames from an automated recording; simply in terms of composition, coloration and focus, you can tell that there is no human interest in their production. As a result I felt detachment from these last photographs where the majority of what had preceded had engaged me.

Throughout the exhibition I sensed a lack of interest in narrative. The images on display were taken quickly or secretly (or both), with the aim being to capture a single, true moment. The act of doing this removes that moment from its context and allows viewers to wrap their own story around it. Every invasion of privacy with which we are confronted is simultaneously an invasion of our privacy and our invasion of someone else’s. Each image of violence invites us to imagine ourselves as victim, perpetrator and onlooker. In some cases, where a set of photos from the same series is presented, a story does begin to take shape – such as that in Enrique Metrinides’ Suicide Rescue from the Top of the Toreo Stadium – but even in these instances the narrative is abstract and incomplete. In this sense the exhibition demands every bit as much work on the part of viewers as some of the “difficult” abstract and impressionist work in the Tate’s permanent collection. For those interested in how the camera has changed our relationship to the world and each other, it is just as richly rewarding.