From Newman, photo portraits of Britain's greats; The Great British, photographs by Arnold Newman, introduction by George Perry. Chicago: University of Chicago Press. $10.

Of all art forms, portraiture may be the most elusive. The face is at once fixed and fugitive. The great portrait plays upon this contradiction as well as a deeper one: the willing conspiracy between sitter and artist. A portrait is very much a shared vanity.

Nowhere is this more obvious than in the formal portrait. The face shaped for posterity flatters both parties. It shows us the sitter as he would likem to be perceived, and, more interestingly, the artist who discerns and consummates that wish.

It's not surprising, therefore, that London's National Portrait Gallery commissioned Arnold Newman to photograph eminent Britons for an exhibition that would later form the core of its permanent collection. Celebrated for his clean-surfaced studies of famous personalities, Newman is one of the finest portraitists working today. And, as an American, he would bring a certain dispassionate clarity to his subject matter, a distance and yet an energy that might elude his British counterpart.

Of the 50 portraits included in "The Great British," we feel the critical eye wonderfully at work. Whether it's Mary Quant or Edward Heath, Newman brings a cool individuality to each study, integrating his subject into a background that further defines him. Shot in color and black and white, the portraits are a visual Who's Who in Britain.

While they succeed as photographs, I'm not sure they always succeed as portraits. With exceptions -- Iris Murdoch looking like one of her tortured characters, or Francis Bacon one of his --the faces are fixed in formality. We know little more about them than before. The problem is not Newman's but that of portraiture itself; its need to present rather than reveal an image.

Perhaps this is why Newman has preceded each portrait with a commentary, detailing his reactions to his sitters and theirs to him. It helps solve the riddle of who lives behind these faces.