Mysterious, even magical – there are few spaces quite like the photographer's darkroom, not least because, with the march of digital technology, it is rapidly becoming part of photographic history. Artist Richard Nicholson has set out to capture these fast-disappearing spaces, photographing darkrooms – and the memories they hold – across London.Richard Nicholson's series feature in the exhibition Analog: Trends in Sound and Picture, at the Riflemaker Gallery , London WC1 (020-7439 0000), until 5 March