The crimson flush of the boldface title on the wall and the darkened boudoir setting suggest that this is a full-blooded seduction – a passionate tale of photographers falling for painters in a big way, of cameras leering at canvases inappropriately. If it is a love affair, then it's a convoluted one, perhaps the complex sort your gossipy friend describes to you involving multiple lovers, break-ups and one-night stands.
The first room looks at half a dozen photographs that take influence from a raucous 1827 scene of rape and ritual slaughter, 'The Death of Sardanapalus' by French painter Eugène Delacroix, which is the original to Tracey Emin's unmade bed and then some. Jeff Wall, one of the world's best contemporary photographers, took the painting as a starting point for his first art-history themed composition, and other shutterbugs have been similarly inspired by the image's heady combination of destruction and sensuality. Rather than a clear exposition of the show's argument about art's enduring place in photography, however, what we get here is something akin to Chinese whispers. This is not necessarily because the photographers cannot do justice to their source material (although they would have failed in trying), but because the Delacroix original is not here to see either, being too vast and too precious to leave the Louvre. The copy, the version, the homage and the inspiration are all hopelessly scrambled.
Then there's the simple portrait of a girl from 2000 based on a Julia Margaret Cameron composition of 1865, which in turn was influenced by the languid, natural style of painters such as Gustave Doré and GF Watts. Are you keeping up at the back? The exhibition's admirable premise is to avoid a reductive ping-pong match of compare and contrast between photography and painting, although Martin Parr's yuppified take on Thomas Gainsborough's land-gentrified couple, 'Mr and Mrs Andrews' is good, clean fun.
Understandably, seeing as the National Gallery are new to this photography lark (it's their first major showing of the medium), they tend to overcomplicate matters and look for obscure lines of influence instead of plumping for the bigger names – why no grandiose Andreas Gursky, no Cindy Sherman self-portraiture, no iconoclastic Andres Serrano, fer chrissakes?
Still, some of the curatorial discoveries are worth making. Obscure Swedish photo-pioneer Oscar Gustav Rejlander is revealed as a master of faux-antique photography and a deft cut-and-paste expert – an 1850s Photoshopper, if you will. Little seen in galleries, Luc Delahaye's war reportage from Afghanistan and elsewhere is represented by two panoramic photos that are every inch the heirs to the National's epic history paintings. The show also reaches safer ground in sections devoted to still life and the landscape, where flat photographs are often no match for even the most minor paintings, the surfaces of which catch the light and sparkle with life.
Just two films of rotting fruit and exploding blooms can compete with the bestilled Old Mastery on display – and that surely is the institution's none-too-subtle point. To return to the seduction analogy, if this were an indecent liaison it would be fulfilling but rather staid, like getting off with your art history lecturer rather than having a fling with a rock star photographer.
If you fancy a bit on the side, then I can recommend finding the interventions scattered within the museum's collection itself, although the bewildered responses of gallery-goers to the sudden interjections of photography are even better. Two Japanese tourists took an age to realise Richard Billingham's ode to Constable was not painted, while a contemporary complement to an Ingres portrait caused one man to believe it the granddaughter of the ancestral inspiration.