`Ironweed' stays on ground, despite stellar acting. Acting talents of film's stars are stretched unglamorously

Nobody questions the acting skill of Jack Nicholson and Meryl Streep, who have proved their brilliance in a long line of varied roles. Their new picture, ``Ironweed,'' calls on them to stretch their talents more than ever - giving up their last shreds of Hollywood glamour to play a pair of homeless winos living on the wintry streets of Albany, N.Y. I'm happy to report that Nicholson and Streep rise heroically to the challenge: Both stars turn in what may be their most vivid performances ever.

Of the two, Streep is the most amazing in her total transformation: Her face is bleary, her gestures are tired and forlorn, even her voice seems to have dropped half an octave under the strains of poverty and misery. Nicholson is more recognizable, but he too pours himself into his role, shuffling along the weary sidewalks like a man who really has reached the bottom of his life.

Not every scene of ``Ironweed'' dwells on the sadness and degradation of Francis and Helen, the main characters. At the beginning of the story, they've been separated for a while, and we see their joy at getting back together - even if the setting is a dingy soup kitchen populated by other alcoholics. The rest of the film shows Francis getting his life in order again, at least part of the way, while Helen slowly sinks under a burden of illness and loneliness.

The screenplay for ``Ironweed'' was written by Pulitzer Prize-winning author William Kennedy, based on his novel of the same title. It's the third volume in his fictional ``Albany cycle,'' each installment of which is more resonant than the last.

The film was directed by Hector Babenco, a truly international filmmaker. Although he calls himself an Argentine, he lives in Brazil and is best known for ``Kiss of the Spider Woman,'' an American movie. He specializes in tales about people who'd usually be considered social outcasts - a homosexual and a revolutionary sharing a prison cell in ``Spider Woman,'' a child prostitute in ``Pixote.''

In his new film, Babenco returns to the kind of down-and-dirty subject that fascinates him. But he also shows the dreamlike turn of mind that produced the memorable fantasy sequences in ``Spider Woman.'' In the movie version of ``Ironweed,'' as in the original novel, the Francis character is haunted by ghosts and visions from the past. These challenge him to overcome the nagging fears and guilts that have shackled his life for years. ``Ironweed'' is one part social realism, one part fantastic reverie - an unusual and risky blend for a star-studded Hollywood melodrama.

I'd respect ``Ironweed'' more, though, if it went even further into the shadowy spirit-world that keeps haunting its hero. Kennedy's screenplay is more tentative than his novel in dealing with this aspect of the story; it gives us only tantalizing glimpses of ghosts and shades before pulling abruptly back into the real world.

Even harder to understand is the decision of Kennedy and Babenco to leave from view the novel's most important supernatural figure, the silent ghost of Francis' dead child. A number of other spooks palpably touch Francis in the film, so why does this crucial one stay out of the picture, except by implication? It's a nagging inconsistency.

I'm sorry the film plays down Francis' visions, because without them, and the insights he gets from them, ``Ironweed'' is just the ordinary story of a couple of sad drunks. It's compassionately written, and splendidly acted by performers ranging from Carroll Baker and Diane Venora to Fred Gwynne and Tom Waits, in addition to the stars. The filmmakers have shown considerable courage, too, in retaining the novel's dreamily ambiguous ending. But at many key junctures, the movie's persistent realism keeps it drifting in the weeds when it could have soared into the clouds.