Built in 1717, Derby's Silk Mill may well be the oldest factory in the world and thus the birthplace of mass production. So it's fitting that the sixth and most ambitious Format photography festival should take as its theme the single word "factory". Its curator, Louise Clements, has chosen to interpret it loosely, with the role of photography itself – the most mass-produced creative medium in the world – at the centre of the festival's exploration of bigger themes such as labour, industry, globalisation, the changing nature of work and the workplace.  Compared with big, extravagantly funded festivals such as the Les Rencontres d'Arles or Photo España, Derby is a somewhat makeshift affair, and all the more refreshing for that. The hub is the Quad building in the town centre, though some of the more intriguing and interactive events are taking place in a disused chocolate factory, as well as the aforementioned silk mills. The festival has two categories: Focus, which has been curated by Clements and her team, and Exposure, comprising work selected from an open submission programme.  In Focus, the centrepiece is Brian Griffin's series of portraits, Still Waters, which feature businessmen and women from Derby. The touchstone here is the city's great landscape and portrait painter, Joseph Wright, whose work captured the dynamism of the industrial revolution in the city. Griffin's staged photographs play with the idea of the grand portrait and the contemporary inflated notion of the importance of the entrepreneur. Unlike Wright's elevated subjects, the successful business people captured here are oddly anonymous, their ordinariness punctured by absurdly mannered poses and Griffin's cinematic lighting.  Griffin's work contrasts beautifully with Chris Coekin's The Altogether, in which Coekin arranges contemporary industrial workers in poses based on 19th-century trade union banners. Again the portraits are lit in a way that heightens their theatricality, and the sense of re-enactment is amplified by a soundtrack of ambient noises which the viewer instigates by playing a seven-inch vinyl record on a turntable. This, for once, is manufactured nostalgia put to politically pertinent use.  Elsewhere there's mischief aplenty, not least in two contrasting displays of found images. Erik Kessels is the undisputed king of vernacular photography curation, and Album Beauty is an ode to the peculiar beauty of the pre-Flickr, pre-Instagram photo album (it's hard to see the factory connection here). Recontextualisation is the defining trait of found photography, as the anonymity of the images is increased, and artified, by the gallery setting. The viewer cannot help but bring their own personal associations to bear on the often odd juxtapositions of images from unknown family albums.  This, of course, is one reason for the power and continuing popularity of vernacular photography, and it's amplified a thousandfold by Thomas Sauvin's extraordinary series Beijing Silvermine 2009-2013. These snapshots of anonymous Chinese people were salvaged from a giant recycling plant on the edge of Beijing, where they'd been sent to be filtered for their silver nitrate content. They cover a 20-year period, 1985 to 2005, and have been selected from a collection amassed by Sauvin of more than half a million negatives. It's vernacular photography on a truly grand scale, as well as a kind of epic, deliberately amateurish farewell to the age of analogue.  For me, the work of the young Ukrainian photographer Sacha Kurmaz proved one of the highlights of the Exposure section. His images of young bohemians and outsiders at play are not for the faint-hearted, but they possess a visceral diaristic power that made them stand out from the more conceptual work on display. Kurmaz describes himself as being from "the beautiful and ugly country, Ukraine", and his photographs capture that love‑hate dynamic.  It was a relief to come upon Elisa Noguera Lopez's surreal and playful series 100 Chickens 1 Egg, joint winner, with Kurmaz, of the Format Exposure award. Against fabric backgrounds, Noguera photographs individual rare-breed chickens on a wooden table scattered with feed. I was baffled, though, by her statement that the series suggested "a personal narrative for the viewer, where resemblance and memories conflate with the visual stimulation provided by the image". If I was a chicken, maybe.  On the documentary front, Pierre Bessard's austere monochrome portraits of Chinese workers convey the on-the-ground industrial reality behind the country's economic growth, as well as the dignity of the people who work in China's huge, often foreign-owned factories. It was great, too, to see Ken Grant's work receiving some attention: his documentary photography from the 1980s, particularly the No Pain Whatsoever series, is from the same great British tradition as the work of Chris Killip and Graham Smith.  Born in Liverpool in 1967, Grant photographed extensively there, and these large black-and-white images of working people at leisure are intimate and arresting, a record of a time when working-class traditions were under threat from Thatcherism. A time when the definition of the word "factory" began to change, and with it our very idea of work.
The sixth Format international photography festival makes brilliant use of Derby's old mills and factories to explore the changing nature of work, writes Sean O'Hagan