Imagine discovering, by some marvel of anachronism, a trunk containing color snapshots of Dickens as a young political reporter or of a debt-pestered Balzac desperate in his garret. To the authors' devoted readers, each frame would hold a near-infinitude of fascination; to uninitiates, a contextless clutter of images.

So it is with PBS' "What Makes Rabbit Run?: A Profile of John Updike," shot last year and airing tonight at 10 on WETA (Channel 26). The producers presume an audience fully familiar with Updike's meticulous, empathic and elegantly rendered chronicles of middle-class angst, tepid suburban lust and muddled spiritual yearnings. The result is less an overview of the artist than a voyeuristic treat for fans.

The hour-long documentary keeps a tight camera on the writer--recording every delicate, near-prissy gesture; every elevation of the ample Dutch beezer; every spoken sentence wrought like written prose--as he endures a publicity tour for "Rabbit is Rich"; stops at his publisher, Knopf; visits his mother on the family farm in Shillington, Pa., where he poses through some household chores, and putters with his second wife, Martha, in the garden of their former home north of Boston. Interpolated throughout are photos from Updike's youth, interviews with family and friends and a running voice-over of the author reading from his work.

Don't expect spontaneity: The same chronic self-consciousness that afflicts his protagonists keeps Updike acting plenty stiff on tape, careful to maintain his genteel reserve. Generally, the intriguing quotes come from others. "He was a luminous boy," says his mother, a hardy L.L. Beanish matron in a knit cap. "He was a grown man before I knew he was a shy person." Just out of Harvard, he "struck The New Yorker like an absolute bombshell" and provoked plenty of hostile envy, says Brendan Gill--and plenty of shock when he fled for the coast of Massachusetts. Provocative stuff. Yet Updike merely maunders vaguely about the debilitating atmosphere of competition in New York: "Not too many writers have emerged from that with their tools still sharp."

But the program offers a wealth of insight-by-nuance. Votaries of Updike's style will delight in hearing him read his sentences in their intended rhythm or watching how, when he starts to laugh, his liquid tenor drops an octave into a ghastly glottal gurgling as if he were trying to clear his throat while choking on Jell-O. Those who recall the often painful ineptitude of his characters will enjoy seeing Updike try to spray a wasp's nest, leaning as far away from it as possible, emitting a little yip of terror when an insect emerges. Those who revel in his lyrical descriptions will enjoy seeing the literal setting of "On the Farm" and "The Centaur," as well as a drive through Reading, Pa., the "Brewer" of the Rabbit novels.

And readers who cringed at Rabbit's anguished relationship with his stammering bungler of a son will be mesmerized at the interview with Updike's son, David--a writer himself, and a gaspingly inarticulate figure with a face contorted by what seems Dostoyevskian woe. He is asked how he felt when Updike pe re limned his celebrated adulteries, ensuing divorce and family wreckage in the "Maples" stories. "He decided at an early age," says David between deep sighs, "that his writing would have to take precedence over relations to real people." Would the son do the same? "I would rather sacrifice a fiction than a friendship. I'd rather not hurt people's feelings if I didn't have to." Updike decorously counters that "my duty as a writer is to make the best record I can of life as I understand it." Besides: "Any age that can make a heroine of Linda Lovelace surely is not an especially privacy-minded time."

But this is to ignore the spiritual purport of his work. And finally, in a moment of rare candor, Updike provides an insight that may seem egomaniacal, but that illuminates at once the novelist's inexorable self-obsession, his godlike role as creator of worlds and the vast compassion of his fiction. "I take the central point of religion to be the confirmation against all material evidence that one immensely matters--that one's sense of oneself as being of infinite value is somewhere in the universe answered."