In the 1920s, Mexico City became a magnet for a new generation of artists and writers hoping to capture the revolutionary spirit in their work. Tina Modotti, a young Italian-born actress, moved to Mexico as a model and assistant for the established photographer Edward Weston. She worked there as a photographer in her own right for only seven years, but during that time she produced some of the most original and lasting images of a society bursting into the modern world with the vitality and hope of the early years of the Soviet revolution. But Modotti not only photographed the revolution, she lived it: from her passionate involvement with prominent artists such as Diego Rivera to her alleged part in the murder of a young Cuban communist leader. Like so many revolutionary artists, she faced a dilemma: do powerful images contribute to change as effectively as direct political action?
It is only in the past 15 years that Modotti has emerged as one of Latin America's most important 20th-century photographers. In 1991, nearly 50 years after her death, the Arles international photography festival in France mounted an exhibition of images produced by Modotti and Weston, alongside their correspondence, which revealed an extraordinary mutual passion not only for each other, but for a still-fresh medium in an unfamiliar country. It was also in 1991 that Madonna bought Modotti's photograph Roses at auction for $165,000.
Today, an indifferent set of Modotti prints is being circulated inviting offers over $1m. The majority of Modotti originals are to be found in US collections, both public and private, and all of the works in the Barbican's new exhibition "Tina Modotti and Edward Weston: the Mexico years", which brings together more than 150 images for the first time, are on loan from America.
Modotti's posthumous success is the result of a small canon of a few hundred images, almost entirely created over a period of six years, by this young Italian immigrant who died (as she had begun) in utter poverty. Tina Modotti was born in 1896, the third of eight children of an itinerant Italian worker who migrated first to Austria, then back to Udine, then on to the US, where one by one the family joined him (Tina when she was 17). Her schooling was so fragmented, and she started factory work so young, that she was largely self-educated. Performing in the popular little Italian theatres of San Francisco and reading literature and history in several languages constituted what she called her "formation".
As a beautiful young actress, she played several small parts in early Hollywood silent movies, but then became entangled with a writer and artist who went by the extravagant name of Roubaix de L'Abrie Richey. He left for Mexico in 1921 and died of smallpox before Modotti could join him - though she arrived in time to find herself having to pay for his funeral, which she did by staging a small exhibition of their artwork.
When she returned to California, she was already in love with Mexico, and by that time she had also fallen in love with the photographer Edward Weston, part of the artistic circle in which she now moved. Together, in 1923, they left the US for Mexico, where they set up a photographic studio. Determined to progress beyond being a darkroom assistant and studio administrator, Modotti dedicated herself to recreating through photography the new world in which she instinctively felt she belonged.
The lovers arrived in Mexico at a time when the country was trying to consolidate after the violent revolutionary years from 1910 to 1917. Rather like the medieval fresco painters, a new generation of muralists were commissioned by the government to teach the Mexican people their history, from its earliest pre-Columbian creation myths to its culmination in a supposedly classless society. The muralists at the forefront of this campaign were Rivera, David Alfaro Siquieros and Jose Clemente Orozco. Modotti was employed to document their work. She was also familiar with the estridentista art movement, which celebrated the speed and inventiveness of the modern world that it was felt Mexico had joined after the revolution. Her own work included studies of such modern - and modernist - subjects as telephone wires, oil storage tanks and factory lines, but also models from the most indigenous regions of the country and its architecture. Modotti joined the Communist Party in 1927, and her compositions combined the personal and political. Most of these images - including her variations on the hammer and sickle using an ammunition belt, an ear of corn and a guitar, and the Red Flag proudly borne by an indigenous Mexican woman - were created for the party newspaper.
Soon Modotti was at the head of every demonstration, often alongside Frida Kahlo and Rivera. At the same time, her naked body was displayed on gallery walls in Weston's photographs and on chapel walls in Rivera's vast mural paintings. The government may have intended politics to replace religion, but it viewed autonomous women with suspicion. Mexican revolutionaries regarded female nudity (and the implied sexual emancipation) as prudishly as the French revolutionaries before them.
By 1930, Modotti's position in Mexico had become precarious. The new government under President Pascual OrtIz Rubio moved to clamp down on the Communist Party, which was preaching that the proletarian struggle in Mexico was not over. Modotti was thrown into jail and then given two days to leave the country. The tabloid press had already found her guilty of shooting her lover, the Cuban revolutionary Julio Antonio Mella, from whose assassination she said she never recovered. (Her homage to him was a photo- graph of his typewriter with a famous quote from Trotsky inserted into the paper feed.)
Denounced as a "foreign political agitator", Modotti became as itinerant as her father, pursuing the revolutionary cause abroad. As she left Mexico, she gave her beloved Graflex camera to Manuel Alvarez Bravo, who became heir to her photographic legacy. In Berlin, she cast her second camera into the river in despair at having nothing to photograph without the light and atmosphere of her beloved Mexico. In Moscow, she gave her Leica to a teenager, believing he would make better use of it than she could, finding herself unable to accommodate either its new technology or the new vogue for "street" photography. And in Spain, she worked herself into a state of serious illness in the thick of the civil war's heaviest battles.
When Modotti finally joined the bedraggled but honourable horde of republican refugees admitted to Mexico after 1939, she was broken in health and in spirit. Some say she died from a long-standing heart condition; others believe she was killed by her Italian lover, the KGB agent Vittorio Vidali. In Mexico, she is remembered as a great beauty and revolutionary who interacted with the country's rich cultural traditions in an entirely new way. In Latin America, she is commemorated in a line that the Chilean poet Pablo Neruda composed for her gravestone: "Perhaps now your heart hears yesterday's rose growing". In the US, her significant commercial value indicates how greatly she is revered. In Europe, she reminds us of her contemporary, the German revolutionary Rosa Luxemburg, who coined the slogan that the poor merited not only bread but roses, too - a belief that Modotti endorsed through her life's work.
"Tina Modotti and Edward Weston: the Mexico years" is at the Barbican Art Gallery, London EC2 (0845 121 6828) until 1 August
Amanda Hopkinson will be giving a gallery talk at the Barbican on 16 June, called "Revolution to Roses: the politics and aesthetics of Tina Modotti's photography"