Francis Bacon: In Camera, Compton Verney, Warwickshire

A show that promises discovery of the private artist finds a man simply in thrall to the photograph

Thankfully, this country-house exhibition is not "Francis Bacon on Camera" – yet another show of black-and-white headshots of the troubled painter – although there are a handful of him on holiday in Athens, in front of a photographer's shop in Soho, or posing in his leather jacket, as was his wont.

No, this is Francis Bacon: In Camera, which translates from the Latin as "in chamber" or "in private". Of course, we already know much of what the notoriously boozy bohemian did behind closed doors, precisely because there was invariably a camera lens pointing at him, recording his every mood and love.

Over and above his friends, models and relationships, photography was Bacon's primary painterly muse. Indeed, so many newspaper scraps, crumpled photos and magazine cuttings have been excavated from the mounds of detritus left on the floor of his old Kensington studio, that scholars have been piecing together, almost frame by frame, the specific photographic references for each painting.

In many ways, the studio was his "camera" – a private chamber of experimentation – where he allowed no one to observe or document him while painting (not even his sitters were allowed to watch after the 1963 triple portrait of Henrietta Moraes, included in this display). Yet Bacon's famously cluttered workspace in Reece Mews is now also his most public bequest, left to us not only in imagery – more of those posed portraits by Cecil Beaton, Henri Cartier-Bresson and others – but in the physical remnants of the studio, now installed permanently at the Hugh Lane Gallery in Dublin, from where much of this show's fascinatingly decrepit stuff has come.

What, then, is this exhibition about? "Francis Bacon and his Chamber of Secrets", or "Bacon the Photo-copier"? In Dubling, this show was titled A Terrible Beauty, which gets us no nearer the truth. It's hard to be clear-eyed about an artist who was so full of his own myth. Better to dive headlong into the material and see which Bacon emerges.

Among the 1,500 photos found in the hoard of paint pots, slashed canvases, postcards and records, a key source was always going to be the early motion-capture stills of Eadweard Muybridge, whom Bacon rated on a par with Michelangelo for his treatment of the human body.

It's never a bad time to look at Muybridge (he'll be getting the full museum treatment later this year at Tate Britain) and the pages ripped from his book, The Human Figure in Motion, were pored over obsessively by Bacon, who spattered them with paint as he placed these wrestling, shadowboxing or exercising nudes centre-stage in his paintings. The sweeping leg in one unfinished work, (Figure with Raised Arm, 1949) suggests that Bacon might have been searching for something in-between Muybridge's sequential snaps that not even the Victorian's rapid shutter could catch: an image, not of motion, but in perpetual motion.

Previously I'd assumed that Bacon's smeared, mangled faces, with their sliding jaws and torqued cheeks, were his approximations of a photographic blur – reproducing the moment when a head swivels or waggles too vigorously to be stilled. Yet these disfigurements (seen in portraits of Moraes, as well as Bacon's lovers John Edwards and Peter Lacy) seem to follow almost precisely the creases, crops, folds and crumples that Bacon, perhaps accidentally, perhaps not, inflicted on his photos, often underfoot on the studio floor.

There's still more of the man and his myth to contend with in the scores of macho bullfighting, footballing and wildlife shots that made their way into other paintings. But even if no fresh view of Bacon surfaces from this soup of influence, then at least he is gradually being seen in a less dazzling, more illuminating light than before. His skewed vision had to come from somewhere – it wasn't an accident of his subconscious as he often claimed. In fact, Bacon eventually began to cannibalise his own images, deconstructing his face from photos, and repainting versions of previous works once they'd been photographed. He, like the child or tribesman who first sees the fixative settle their image for ever, was simply in thrall to the photograph. That was his dirty little secret.

Compton Verney, Warwickshire, to 20 June (01926 645500)

Ossian Ward is visual arts editor of Time Out