Heavy-lidded, bare-footed, she reclines on a gorgeous sofa in a brocade robe, her lazy gaze fully exuding the heavy sensuality that drove her poet-lover, Quais Ibn al-Mulawwah, known as Majnun, mad. With one hand she strokes a leopard skin; the air is thick with the scent of lilies. Is Leila cruel - or is she merely bored? A woman who knows and exercises her power, or just an idle odalisque?

Sir Frank Dicksee's 1892 vision of the classical Arab temptress is one of the treats to enjoy in Tate Britain's new show, The Lure of the East, which brings together more than 100 paintings and drawings of the Ottoman empire by British artists and ranges them by theme (religion, gender and genre, portraits). The pictures range from the eye-rolling to the outstanding, but it's a visual feast and the lure is much in evidence: harems, bazaars, camels, mosques and turbans abound. What is not so obvious is how the Orientalist designation applies to artists such as Augustus John, or even Dicksee himself, who painted fashionable ladies in his studio in St John's Wood.

We're on firmer ground with the star of - and original inspiration for - the show, John Frederick Lewis, who made a triumphal return to the London art scene in 1850 with his exquisite watercolour The Hhareem [sic] - a picture sadly too fragile to travel with this exhibition. From the title's superior sort of spelling, down to the gorgeously minute detail of fabrics and objects, Lewis makes an appeal to accuracy that runs counter to the faintly absurd subject matter of the painting, the introduction of a new odalisque into the harem of an Ottoman gentleman, who sits gaping with eager astonishment. Lewis was not the first English artist to go to the East, but he was unusual in settling in Cairo for ten years from 1840, where he worked on his sketch books.

The British were about to fall in love with the Middle East. For one thing it was quite easy to go there by the 1840s, so that the sort of journeys that Byron had made so much of became almost everyday. David Wilkie, it's true, didn't make it home: his death aboard ship was commemorated in Turner's Peace - Burial at Sea. Richard Dadd came home only to murder his dad, afterwards pursuing his career inside Broadmoor; but others, such as David Roberts, managed to lash themselves around the sites in short order. Even Edward Lear was able to roam from Albania to Petra and get home safely. By the 1860s you could visit Palmyra with Thomas Cook.

As Lure of the East demonstrates, this is the period when British artists began to record their own responses to the Ottoman world; earlier painters had merely plundered the dressing-up box. Gavin Hamilton's 1758 James Dawkins and Robert Wood Discovering the Ruins of Palmyra puts the explorers in togas and buskins, beside an exotic Eastern medley of camels and turbans; almost a century later, David Wilkie instead focused on form and gesture in An Arab Muleteer.

Echoing the spirit of Lady Mary Wortley Montagu the previous century, some commentators compared Eastern freedoms favourably with the industrial slavery of Victorian England. That attitude is reflected here, a foretaste of Pre-Raphaelite enthusiasm for “honest” medieval simplicity.

There was a receptive audience for this stuff at home, as Thackeray said. “There is a fortune to be made by painters in Cairo... I never saw such a variety of architecture, of life, of picturesqueness, of brilliant colour, of light and shade. There is a picture in every street, and at every bazaar stall.” Lewis, whom he championed, really did it best: he may have recycled the same stuff for 25 years after he came home, even trying the patience of Ruskin, who had first encouraged him into oils, but he did it with a shy sense of irony. Both in The Carpet Seller and in Interior of a Mosque, Afternoon Prayer (The 'Asr) he renders a disguised self-portrait, once as the carpet dealer, the other as an old military man about to pray, which seems to exude a private yearning for fellowship with a world he could, when all is said and done, only watch from the outside.

William Allan's The Slave Market, Constantinople is one of the show's disappointments; the surging and sighing feels lumpish, and pales into insignificance against Jean-Léon Gérôme's bold and nasty For Sale: Slaves at Cairo, which was shown at the RA in 1871 because Paris was under siege. British critics drew back, shocked. For Sale was kinky and ahistorical, and its bright, highly varnished surface detail was like pornographic lip gloss - putting the critical establishment of 1871, as the show curator Nicholas Tomkin wrily observes, plumb in line with late 20th-century feminist criticism.

Following Disraeli, maybe, Britons fretted about biblical truth and the history and destiny of the Jews; many painters were lured to the Holy Land. Holman Hunt took a muscular Christian view of it all, and his riposte to the woman problem - all that veiling and subtlety - was to paint the deliciously absurd but beautiful The Afterglow in Egypt, showing a dusky girl adorned with wheat sheaves, healthy, bronzed, unveiled, open and sexy in a kibbutznik sort of way. But though Hunt did visit, and paint, the Holy Land, you feel that we are already stepping out of what might legitimately be described as Orientalist, and entering a private world of religious imagery that might just as well have been concocted in Hampstead as in Jerusalem.

The show ends with Richard Carline's picture of Damascus from the air at 10,000ft, made in 1920, when the British moved from propping up the Ottoman Empire to trying to sort out its remains, a bodged process whose consequences are still being felt, 10,000ft below.

The Lure of the East: British Orientalist Painting is at Tate Britain, London SW1, from Wednesday, until Aug 31 (020-7887 8888; www.tate.org.uk)

BEST IN SHOW: THE HIGHLIGHTS OF THE LURE OF THE EAST

Lady Mary Wortley Montagu in Turkish Dress with a Page

Lady Mary Wortley Montagu (1689-1762) travelled to Istanbul with her husband in 1717 and published her Turkish Embassy Letters in 1719. She was the first Westerner to give a full account of the harem, and provocatively suggested that Ottoman women were freer in many ways than their European sisters. This portrait, believed to date from 1725, is attributed to Jonathan Richardson (1667-1745).

Seated Man with Chibouk

Richard Dadd (1817-86) travelled through the Middle East in 1842, but spent the remainder of his life locked up in mental asylums after killing his father. All his life he continued to paint, drawing on his sketchbooks from his Middle Eastern tour. This quizzical portrait was only recently identified as his work.

Damascus and the Lebanon Mountains from 10,000 Feet

Richard Carline (1896-1980) became an officer in the Royal Flying Corps in 1916. Three years later he was posted to the Middle East. This powerful view of Damascus from 10,000ft, painted in 1920, might suggest the fragility of human endeavour; the city and its mosques are tightly packed against the backdrop of the desert hills.

Hhareem Life, Constantinople

John Frederick Lewis (1805-76) lived for ten years in an elegant Ottoman house in Cairo, returning to England with the sketchbooks and artefacts that sustained the remainder of his career. His detailed, sometimes enigmatic, work forms the core of the exhibition. This work dates from 1857.

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