Portraiture as theater. Sir Joshua Reynolds The artist's subjects often became fancy-dress figures from history and mythology as Joshua Reynolds (1723-92) combined quotation from the paintings of the old masters and his own fertile inventiveness and sense of humor.

`THE genuine painter, instead of seeking praise, by deceiving the superficial sense of the spectator, . . . must strive for fame, by capturing the imagination.'' So observed Sir Joshua Reynolds in one of his ``Discourses'' as first president of England's Royal Academy of Arts just over two centuries ago. Reynolds certainly strove hard for fame. And even in what might easily have been the dull routine of portraiture, he aimed to capture the imagination. The large exhibition of his work at the selfsame Royal Academy -- here through March 31 after its initial showing in Paris -- shows that he had a considerable imagination, even if it could be self-conscious.

Although he now and then painted at high speed and was cursory or careless about his backgrounds, and though he was almost perverse in his use of disastrously impermanent materials, he did practice what he preached by striving to make portraiture much more than a matter of superficial praiseworthiness. He wanted visual art in general elevated to what he called a ``true dignity,'' like poetry. He wanted it to be of the mind rather than the senses.

He aspired to be a ``history painter,'' but it was only toward the end of his career that he managed some large-scale works that qualify -- paintings such as ``The Infant Hercules,'' a subject he chose for a ``historical picture'' commissioned by Catherine II, Empress of Russia. This mammoth mythology from Leningrad was last seen at the academy in 1788. Its sublimity and imagination are unquestionable, though marred now by deterioration of the sort Maria Edgeworth witnessed in 1831 when she wrote that one of his self-portraits was ``all going -- risen in great black cracks and masses of bladdery paint.'' Its state makes it hard to see today. In any case, it's not easy to appreciate how such a grandiose concoction could have seemed to Reynolds more ``genuine'' as a species of painting than his portraits.

Not that all his portraits could be described as modest. Socially speaking, his sitters read now like the roll call of a charity ball reported in Harpers and Queen, the English equivalent of America's Town & Country: ``Lady Charles Spencer in a Riding Habit,'' ``Viscount Milsington,'' ``The Hon. Charles Sloane Cadogan MP,'' ``Miss Sarah and Miss Elizabeth Crewe,'' and so on. Life size and full length, they were designed to hang in great country houses and to maintain or raise the status of the sitter. Reynolds's style was equal to such heights and ambitions. Nicholas Penny in his catalog essay for the show quotes a contemporary amusingly shocked to see the features of his ``half witted'' acquaintances painted so that ``every muscle in their visage appears to be governed by an enlightened mind.'' As for Reynolds's female sitters, he painted them as ``ladies'' even when they were not.

But social superiority alone clearly did not satisfy him even in his portraiture, and by means of a mixture of quotation from the paintings of admired old masters and his own fertile inventiveness, he transformed his subjects not only into fancy-dress hussars and shepherdesses, but into ``Psyche'' or ``Euphrosyne,'' the huntress ``Diana'' or the ``Comic Muse.''

Nicholas Penny suggests that we should not take all this too seriously, and it is certainly difficult to do so when we learn that Lady Sarah Bunbury was not, in real life, at all the kind of woman to be caught ``Sacrificing to the Graces'' (she preferred playing cricket and eating beefsteak); or that Miss Kitty Fisher -- a renowned courtesan much painted by Reynolds -- was notoriously voracious and this is why he depicted her, with her apparent approval, in the character of Cleopatra dropping an enormous pearl into a chalice of wine so she could drink it dissolved.

Reynolds knew that such a ``great style'' was high artifice, and his own early caricatures show that he was aware how close the contrived sublime comes to the absurd. But when he pulls it off in his allegorized portraiture, he does so with much elegance. Perhaps the most successful work of this type is the gracefully balletic picture of ``The Montgomery Sisters: `Three Ladies Adorning a Term of Hymen.' ''

Such a painting really turns portraiture into theater, and Reynolds is obviously at ease when painting actors and actresses like David Garrick and Sarah Siddons: He celebrates and relishes the art of performance. Perhaps it is a similar enjoyment of acting, or acting the goat, that drew him with undisguised delight to the portrayal of small children. These pictures have been severely criticized, but they add to a comprehension of the artist and show an ingenuous side of him which deserves better than scorn.

It is, however, in his portraits of the literary men with whom he mixed -- Samuel Johnson, James Boswell, Oliver Goldsmith, Giuseppe Baretti -- and in his own self-portraits when they are least pretentious, that the spectator today finds him most intimate and sympathetic. The art historian R. H. Wilenski credited Reynolds with such a bad character that he accused him of ``exploiting'' his writer friends. But both exhibition and catalog here suggest otherwise. Here were men he felt he could paint without pretense or compromise.

Occasionally one of his society portraits strikes one with the same forthright integrity: ``Anne, Countess of Albemarle'' looking up sharply from her ``knotting,'' for instance; or ``Mary, Countess of Bute,'' parasol in hand, out walking her dog. The latter painting, on public exhibit for the first time in a century, is almost a foretaste of Manet in its directness.

The portraits of Johnson and Goldsmith, however, speak more deeply of reciprocal appreciation and friendship. Johnson influenced the painter's thought and writing; he also praised him ``as the most invulnerable man he knew.'' And when Goldsmith died, Reynolds was so upset that he didn't paint for an entire day. Which says as much about his regard for his friend as it does about this industrious artist's exceptionally dedicated working habits.