Tacita Dean, FILM, Tate Modern

Tate Modern’s lofty Turbine Hall is dominated by a giant CinemaScope screen flipped on its side so it becomes 42ft high and resembles a lift shaft or cathedral window. Instead of angels, saints or sinners, though, the starring role in Tacita Dean’s FILM is given to the building’s east window – the one hidden behind the huge screen. One of the main subjects of the film, then, is the very spot where you are standing – where much of the film was shot.

On film, the familiar glass and steel structure plays host to images culled from the outside world such as fountains, waterfalls, lakes, the sea, trees, a smoking industrial chimney, an escalator, flowers, mushrooms, pigeons, a snail and a grasshopper; add to this abstract patterns and surreal incursions such as an eye, balloons and a light bulb, and you get an apparently random sequence of mesmerising visual effects lasting just 11 minutes.

"FILM (pictured right and below) is basically a collage," Dean explains and she means it literally. The images took shape as collages made by cutting up postcards from her vast collection; she surrounded the Matterhorn with sea, for instance and, on screen, the idea is transformed into a peak rising above swirling mist.

Making a collage with scissors and glue is one thing, but producing similar effects on celluloid without resorting to post-production wizardry is a huge challenge. To introduce the variously shaped inserts she wanted, Dean had to design circular, elliptical, square and triangular masks that fitted between the film and lens to conceal some parts of the frame and expose the rest. And to construct each frame one element at a time meant putting the film through the camera up to 10 times.

She also revived techniques such as glass matte painting; to mimic lightning, she painted a jagged line across glass and shone a light through it. Hand-tinting turned black-and-white footage blue, orange, cerise or pink and allowed an eight-second shot of mushrooms to appear in six different colours. Finally, down the side of each frame she added sprocket marks so that on screen the image looks like a strip of film held up to the light. Not surprisingly she describes FILM as a portrait of film that pays homage to the medium.

"FILM," she writes, “is a visual poem. I found the rhythms and metre from the material itself, relying not only on the images I had but on what is normally considered waste: the picture fading at the end of a roll, the shimmering metamorphosis of a filter change and the flash frames of over-exposure as the camera stops and starts. FILM is about film and in the end I let the material’s intrinsic magic be my guide.”