A NEW biography of George Chinnery, the most talented Western painter to have worked on the South China coast, is an event worth celebrating. Only two previous attempts at his biography exist, both more notable for inaccuracies and an amateur approach than for any real merit. Patrick Conner brings to the task his skills as an art historian, and also a certain balance and sense of humour appropriate to the subject. He begins by demolishing the fog of myth surrounding Chinnery's life, allowing the robust, down-to-earth character of the painter to make its historical contribution. The teenage Chinnery attended the Royal Academy in London and at the age of 19, had paintings in the academy's 1793 exhibition. Surprisingly, for a youth set on success in the capital, he soon migrated to Dublin where he busied himself with portraits and miniatures, and married Marianne Yigne, his landlord's daughter, with whom he had two sons. What occurred in the marriage we do not know, but Chinnery abruptly left Dublin for London, and shortly after left for Madras. On balance it seems he was disenchanted with his wife. Years later in Macau, he remarked that: ''Mrs Chinnery's appearance cannot be exaggerated. She was an ugly woman 30 years ago: what in the name of the graces must she be now?'' Yet his portraits of her show a demure girl with fine eyes. The progressive truth of his self-portraits over the years reveals himself as a fleshy-faced man with a top-heavy brow and wet, pouting lips, features that became more pronounced as age increased. He had, it might be said, little room to complain of ugliness. From Madras, where he first landed in India, a move to Calcutta, then capital of British India, was a natural one. There as portraitist to the society of the day, he earned richly and spent extravagantly. Then, to escape his creditors, he took a ship to Macau where he was to spend the remaining 27 years of his life. Patrick Conner draws an entirely credible portrait of Chinnery the man and the painter, a composite of endearing and exasperating traits subservient to a ruling mania to draw and paint. The portrait is easily the best researched, and best psychologically understood likeness that we have of him. This is matched by Conner's analysis of Chinnery's painting. Of Chinnery the artist there are several aspects: his compulsive drawing, exercised daily throughout life; his gifts as watercolourist, greater than his skills with oil paint; and his importance as the most prolific and talented documenter of the China coast and its society, both Western and Chinese. Unique in the annals of his time, he remained an 18th century painter into the middle of the 19th. As a portraitist, Chinnery is by turns both fascinating and a disappointment, his interest centred on the face. Having caught the character in it, his interest faded so that few of his full-length figures reward scrutiny. His drawings attest his skill in rendering hands and feet; his oils seldom. In fact he was a portraitist by economic necessity. Yet, some clumsiness aside, Chinnery's are the best records we have of Westerners - ruffian commercial traders, men such as ''Gutz the missionary'' facilitating opium sales, who ''travelled along the China coast as an undercover agent for both Jardine and Jesus''. Notably his portraits of the great Chinese merchants are some of the best ever painted. It is his drawings and watercolours, and this volume contains many of both, that show Chinnery at his best. He captures on paper the thousands of Chinese he saw around him daily, in drawings of unmatched clarity and candour, unequalled by any other artist in the East. The watercolours catch the unique qualities of light as the sun rises on innocent mornings and declines on soft evenings along the China coast. No one has shown better its visual and sensual beauty. In India, his country scenes show us similarly, the essence of a very different land. The virtues of Conner's Chinnery book are many. Having severed myth from fact he uncovers the man - querulous, ugly, compulsive, testy, often penniless when not scattering a fortune to the Calcutta winds. It is a roundly credible portrait with none of the artist's disdain of the hands and feet. The very generous illustrations offer a view unique in any published source of Chinnery's output. If one has a complaint it is that none of those pictures is accompanied by its dimensions. And the index where entries are followed, simply by a string of page numbers, is less than helpful to the student of the subject in a book which deserves serious study. GEORGE CHINNERY 1774-1852: Artist of India and the China Coast, by Patrick Conner (Antique Collectors' Club, $895).