Minnie Weisz: I am a camera

Minnie Weisz chose King's Cross, in London, for an extraordinary project that harnesses the photographic power of whole rooms. Simon Hardeman meets her

There's a fascinating contrast between the recent activities of the actress Rachel Weisz and her artist sister Minnie. While the Oscar-winner makes her living courtesy of ever-bigger-budget, hi-tech camerawork in movies such as the Mummy series, Minnie has turned to some of the oldest, most rudimentary optical technology. Her latest show features photographs of rooms in the now empty 1854 Great Northern Hotel in London, and in most of the images she has turned the spaces into giant pinhole cameras.

Her exhibition, King's Cross as Camera Obscura, has been mounted as part of this year's London Architecture Biennale. Organisers chose the theme of "change", and one of their examples of this is King's Cross, which is in the middle of a multi-billion-pound, 20-year, transformation from a grimy and dilapidated confluence of road traffic, sex-workers, and commuters into a shiny, happy, fresh development with new homes, shops, schools, and a range of leisure facilities.

Minnie Weisz is slim and pretty, and full of energy. Dark haired, and in a simple dress, she laughs frequently as she tells me that, as a lifetime north Londoner, she has always been fascinated by the area. Her book and exhibition Eye Dream, last year, featured a series of photographs of romantic, redolent emptiness and dignified decay inside the mid-19th-century Fish and Coal building close to the busy station. Indeed, the idea for this show came from her work there.

"The magic moment was at Fish and Coal", she says in a voice that she shares with at least one other member of her family. "After I was there for five days I realised I was in a camera. I was there, with my camera, in a camera."

Weisz is, after all, the younger sister of someone who makes her living as, effectively, a projection. Born in London's Hampstead Garden Suburb 30 years ago, she spent most of her childhood in Hampstead itself, along with Rachel and her step-brother, and she still lives nearby.

She has a passion for film; as a child she would go to the cinema every Saturday morning ("I saw all the Lassie films, and lots of Bette Davis, and things like The Nutty Professor); and studied at the Royal College of Art and the London College of Printing - she has two degrees and an MA - but it was while doing a German degree in Berlin that she became intrigued by two of her now recurring themes. "It was only three years after the wall fell, and there were all these derelict buildings. At the same time, there were strange private art events, upstairs in people's lofts, or in cellars."

A few years ago she recorded her own private performances when she made a film called Urban Fairy Tales, in which she documented people's reactions to circus acts that appeared unannounced in their south London tower block.

For her latest "private performances" she has taken empty rooms in the Great Northern - the first great railway hotel in England - turned them, literally, into cameras, and then photographed the results. The images show not only the rooms, as she had in the Fish and Coal building, but also imprint on them the outside, the disappearing present-day King's Cross and its redevelopment. And all of them are in a process of flux.

"What you get is like transience within transience. It's like a Russian doll, with one layer inside another," she tells me. "The hotel is marooned in King's Cross, surrounded by construction and regeneration. It's a nowheresville. But for me it's about humanising these buildings. I show them and they show me." Show you? "Show me things, about themselves," she corrects.

The technique is simple. "You just black out the windows with paper or whatever, and make a pinhole. And then you're inside a camera, with the image of the outside projected in it. You can see people walking over the ceiling. It's quite eerie."

What was also eerie was wandering around the empty hotel. "Sometimes I'd find myself on the fifth floor and it would look exactly the same as the floor I was supposed to be on and I'd be totally lost. Until I saw a dead pigeon that wasn't on the floor I was supposed to be on," she laughs.

"It's a romantic subject," Weisz sighs. "All these huge, looming buildings, and now they're empty, where once it was about so many people arriving and leaving". She sees herself as a detective, inhabiting buildings to uncover their souls. One of the photographs, "Room 418", is particularly disconcerting: you don't immediately notice that it is upside-down because, in this state, the projected image appears the right way up. The flat roofs of what look like railway sheds hover over the floor like a daylight hologram, and a wire coathanger rises, from a hook, like a cheap aerial.

But perhaps the eeriest image is "Room 413", where the inverted neo-gothic towers of St Pancras seem to drip down the walls like liquid claws enveloping the sad, lonely, space, heading towards a pair of shoes and a dead pot plant. In another, a blurry corner of a dingy room houses a pair of suitcases and a cushionless chair. This one has a proper title: "Pinhole Noir," she announces, not entirely seriously.

Her photographs of the projections also feature objects she found lying around the old place, one-time mundanities that now have the status of relics, heightened when the unsuspecting outside world is projected on to them. The pigeon isn't in evidence, but there are old brown shoes, various suitcases, and pictures and posters, some of which she arranged on one room wall, above a cheap bed-end. "It's what I call a merry wall! A little shrine."

Not all the photographs in the exhibition feature projections. Some, like this "little shrine", appear to be simply of empty rooms but, on closer analysis, often include a dialogue between found elements within them - a pair of ladies' travelling cases, for instance. "It's about self and others, connection between things," muses Weisz.

Another layer of connection, of transience, is the venue for King's Cross as Camera Obscura. It's a further example of the obsolete, decaying, past: the Albion Stables, just north-east of the railway stations. Here horses were kept upstairs, while trams were manhandled downstairs; once it was the very hub of transport in an area born of transport links, and defined by the effect travellers have had on it. And now, amid its whitewashed emptiness, hang photographs of nearby defunct interiors, festooned with images of the corresponding, similarly doomed exteriors.

And in a damp corner, on a tea chest, sits Minnie Weisz, planning her next move. She says she wants to go to Istanbul and, maybe, even Shanghai, to do something similar. "My goal is world domination by camera obscura," she guffaws. "I want buildings watching each other across continents!"

Kings Cross as Camera Obscura is at The Albion Stables, Balfe Street, London N1 until 5 July ( www.londonbiennale.org.uk)