Where photographs were most like paintings was in the fact that both required generous amounts of time: while the application of paint on canvas was necessarily laborious the long exposures required by early cameras (often needing several minutes) meant that subjects needed to be static. Portrait sitters would have to hold a pose, often supporting themselves with a table, chair or hidden metal armature to keep themselves still and not blur the plate. Roger Fenton's celebrated photographs of the Crimean War have a carefully composed feel precisely for that reason. He was not able, as today's      photojournalists are, to capture battle action so his compositions resemble the static military paintings of Horace Vernet. His soldiers, though real, have to pose every bit as carefully as an artist's model.

Long exposures meant that other painterly genres such as landscapes, still lifes and the nude were natural topics for photographers too. This last, however, had to face the problem expressed by Henry Peach Robinson in the 1850s: "The nude is the divine ideal; the undressed is the modern naked girl." To overcome the accusation of showing simply naked girls, photographic nudes had to ape paintings. There was nevertheless an active market for nude photographs that had nothing to do with noble appreciation of the human body — as what the painter Delacroix, an admirer of photography, described as "this admirable poem" — and everything to do with carnality. The work of     modern photographers such as Robert Mapplethorpe and Nan Goldin show that such issues have not gone away.

The third strand of the exhibition is intended to show the ongoing influence of the first photographic generation. The exhibits leap almost the whole 20th century and the selection of photographers is carefully weighted. There is no Andreas Gursky for example, the world's most expensive photographer, nor William Eggleston or Richard Prince, all of whom can be intensely photographic. In their place are the Israeli Ori Gersht, whose Blow Up showing an exploding vase of flowers is placed alongside 19th — and 17th — century flower paintings by Fantin-Latour and Balthasar van der Ast, and Richard Learoyd, whose dorsal portrait of a man with an octopus tattoo is the companion piece to Ingres's sinuous painting of Angelica Saved by Ruggiero. 

Beneath their postmodern knowingness such images demonstrate how the pictures made by Fenton, Cameron et al preserved the photographer's spirit as well as the parade of 19th-century faces they put before their lenses.