Harry Callahan, Tate Modern

Tate Modern display: Harry Callahan is little known in the UK. This exhibition highlights his importance as a post-war pioneer.

As part of Tate Modern's cultural mandate, every year the museum spends around £1 million on new acquisitions to add to the permanent collection. Given the robust state of the art market, with works by the most desirable artists consistently auctioned for way above their estimates, £1 million is not an awful lot to play with. For that reason, Tate's collecting has tended to focus on mid-career contemporary artists whose work is still relatively cheap. However, in 2009 the Tate set up a committee to address the lack of twentieth century photography, and one result was the acquisition of 90 works by Harry Callahan, an American photographer who has had little global exposure. 

Callahan lived in Detroit, Chicago and New York. He married young, had one daughter, and the family summered at Cape Cod and Lake Michigan. A prolific photographer, he spent each morning walking and taking pictures, and each afternoon going through the negatives and printing. Callahan began his photographic career as an amateur enthusiast. He was not technically trained and, although he experimented with double exposures and other techniques, the real charm of his photographs lies in their ordinariness. They are personal and domestic, showing a life amongst other lives. 

The commercialisation of photography, which enabled it to transition from a specialised technology to a ubiquitous one, made it possible for an unprecedented number of people to start producing images. Callahan's subject matter – city streets, his wife and daughter, the beach – doesn't necessarily differ much from that of anyone else's amateur photographs, but he does display a remarkable feel for light and composition. His eye picks out an ordinary blade of grass, or some people going to work, and transforms it into something of beauty. 

Tate's acquisition of Callahan's work celebrates a model of the artist who is not necessarily a genius possessed of extraordinary powers, but an enthusiast who works hard. Although Callahan took many pictures every day, he only selected a few to become artworks.