FRANCO Zeffirelli's "La Traviata," probably the most successful film of an opera, reaches an emotional intensity even beyond that found in an opera house.

The story is generally acknowledged to be based on Alexandre Dumas' affair with the fabled Marie Duplessis. When she died in 1848, Dumas made their romance into his novel, "La Dame aux came'lias." Four years later he rewrote it as a play, which the next year became Verdi's "La Traviata." Ever since then, the Lady of the Camellias has been a prime vehicle for tragediennes with a flair for 19th century Romanticism--Bernhardt and Patti and Garbo and Callas among them.

Now comes Zeffirelli's movie, with Teresa Stratas as Violetta, a performance of heartbreaking power. Stratas builds a cumulative emotional tension that is riveting. As Violetta is battered again and again by unexpected blows, the dying courtesan is, by turns, brazen, capricious, tender, noble, compulsive, afraid and--always--vulnerable. Acting and singing become inextricable. And the youthfulness of her beauty is never an issue (even though Stratas is actually 44).

Zeffirelli has lavished everything on this movie, which opens today at the West End Circle. The sets for Violetta's party, which opens the opera, and for Flora's party, at which Violetta and her lover Alfredo (played by Placido Domingo) confront each other after the rupture of their relationship, look like preliminary studies for the Paris Opera. Zeffirelli even brought in two Bolshoi dancers, Ekaterina Maksimova and Vladimir Vassiljev, for the brief ballet sequence at Flora's party.

All this extravagance serves to intensify and clarify the ominous dramatic currents, the ironic contradiction between Violetta's addiction to "life as a celebration" and her passion to be truly loved before she dies. The romantic scenes are sumptuously visualized in the sensuous bucolic montages when Violetta and Alfredo escape Paris for a life of pastoral bliss. These are in impeccable taste, but there are a few too many of them.

Zeffirelli may heighten the effects, but he does not tamper with the opera. Sometimes the film approaches the surreal, but in this movie Zeffirelli's sense of pacing is sure: He never allows digressions to impede the accelerating tension or trivialize the drama. The cameras concentrate so intently on Stratas that the grandeur never threatens her commanding presence. This is Zeffirelli's finest film since "Romeo and Juliet," for which he won an Academy Award as best director.

The passionate character of Alfredo is too much of an insensitive cad to give full vent to the sonorous nobility of Domingo at his greatest. It is an ardent, svelt, gracefully acted and beautifully sung Alfredo--and, by contrast with most other tenors, his physical appeal is obvious.

Alfredo's father, Giorgio Germont, who interrupts their life in the country imploring Violetta to leave Alfredo, is sensitively played and sung by baritone Cornell MacNeil. His shifting moods toward Violetta, from initial hostility to compassion to (at the end) guilt, are sharply contrasted. Their initial scenes, especially, are superbly done.

With James Levine conducting the Metropolitan Opera orchestra and chorus, this is very much a performance as you would see it at the Met today, except for Stratas. She is a major Met star, but she had never sung Violetta at the Met and, in fact, when the film was made in Rome last summer, she had not sung it anywhere for 12 years. Her voice is a bit slender to do it in a large house. This was no hindrance in the film, though once or twice there are rough moments. It is sung in Italian, with subtitles.

Except for Stratas' singing, the splendid musical performance was taped entirely in New York before shooting began in Rome at the studios of Cine Citta . Most of the time, the characters lip-sync with the tape, not always precisely, and occasionally they sink into dreamy reveries while their singing on the tape goes on--a dubious practice. The sound track, for all the wizardry involved in the film, is not entirely satisfactory. The voices are recorded close and dry. The orchestra is distant and reverberant.

The cumulative force of "Traviata" gains tremendously from being played without intermissions for set changes. Zeffirelli builds the tension gradually. During the opening credits, the film starts, astonishingly enough for an opera, with total silence, as the camera surveys Paris rooftops on a gray day. It dips to Notre Dame, a bell tolls, a carriage passes, and then we are at the site of Violetta's palace.

Only now does the prelude begin, with the soft, sad theme of despair in the high violins. Inside the palace, shutters are closed and furniture and objects are covered in sheets. Violetta's maid, Annina (Pina Cei) passes in the hall with a priest. A handsome young apprentice porter looks through a door and spots the dying Violetta lying immobile on a bed. He takes off his cap and withdraws hurriedly (Zeffirelli uses this character as a symbolic figure several times in the movie).

The prelude comes to its second lyric theme. Violetta wakes, coughs, wearily rises and goes to the door, looks down the hall, and begins to hallucinate about the parties that have been held there and the movie goes into the first act of "Traviata," the gala at which the principals will meet and fall in love. The tension reaches a near breaking point in the turmoil of Flora's party. Then it breaks into the tragic, intimate denouement of Violetta's death scene.

Proust once remarked that in "La Traviata" Verdi had lifted "La Dame aux came'lias" "into the realm of art." That is what Franco Zeffirelli brings us in this film. LA TRAVIATA

Directed, written and designed by Franco Zeffirelli; conductor and music director, James Levine with the Metropolitan Opera, Orchestra and Chorus; original music by Giuseppe Verdi; art director, Gianni Quaranta; director of photography, Ennio Guarnieri, A.I.C.; edited by Peter Taylor and Franca Sylvi; produced by Tarak Ben Ammar. An Accent Films presentation. This film is rated G. THE CAST Violetta....Teresa Stratas Alfredo....Placido Domingo Germont....Cornell MacNeil Baron....Alan Monk Flora....Axelle Gall