TV about TV is still fairly rare; the medium tends to ignore its own existence. Thus tonight's NBC movie "Extreme Close-Up," at 9 on Channel 4, is especially to be welcomed for its imaginative and ambitious relevance.

Originally titled "Home Video," the film is essentially the story of a 15-year-old boy who retreats into video images of his family's past after the mysterious death of his mother. In a way -- but only a way -- it's a telefied update of Samuel Beckett's 1958 play "Krapp's Last Tape," about a man submerged in audio recordings of his life, in the process forgetting to live.

Unfortunately, the concept of "Close-Up" gets a little clouded. The boy does withdraw into electronic images, and he plays scenes from his video scrapbook over and over -- looking for an explanation for his mother's death -- but he also takes the camera to school and makes lively, even funny tapes about teachers and fellow students.

So, is he withdrawing, or isn't he? The script equivocates, but that doesn't by any means drain the film of interest. It was written by Marshall Herskovitz from a story he dreamed up with partner Edward Zwick; they're the creators and coproducers of ABC's "thirtysomething." Peter Horton, who plays Gary on that show (a character reportedly to be killed off this season), directed, doing a very good job of jumping from the filmed story to the young hero's videotape inserts and back.

"I'm sorry about your mother," a girl tells the young man in a school hallway. The moment becomes an instant replay as he studies it at home. These shifts from reality to replicated reality keep a viewer attentively off guard.

As one might expect from this particular creative team, "Close-Up" scores big on the old sensitivity scale, but not in the self-congratulatory way "thirtysomething" sometimes does. There is trenchant contemplation of how technology can alter basic concepts and consciousness.

"You shouldn't live your life through video, David," the father lectures his son. "I'm not living my life through video," David replies. "I have no life."

As David, promising novice Morgan Weisser is one of the best reasons to watch the film. He circumvents the cliches and yet continues in the screen's noble tradition of tortured youth. His initially platonic friendship with a sympathetic girl at school -- Samantha Mathis, another fresh discovery, as Laura -- evokes memories of James Dean and Julie Harris in "East of Eden."

And evoking memories is what this picture is all about.

Unfortunately, the rest of the family is not in Weisser's league; he deserves better. As Dad, Craig T. Nelson, the blank wall on which very little has ever been written, doesn't give many clues as to how one is supposed to feel about the character. Is he a hardhearted clod, or simply a passive cipher? "What do you think I am," he asks David, "the most callous person on the face of the Earth?" Hmm. Could be.

Blair Brown, on the other hand, mercifully modulates her usual cold coyness in the role of the mother, who is seen only in David's videos. Herskovitz and Horton do a good job of laying down the portents -- the worsening mental illness that makes the mother more and more unreachable to her family -- but when it comes time to dramatize her death, the result is unfortunately anti-dramatic almost to the point of being ludicrous.

Misgivings aside, "Extreme Close-Up" is still substantially more intelligent than 95 percent of the movies networks make, partly because, unlike most, it truly is based on an actual idea.

It also proves that when TV looks at itself, the result can be something other than studio audiences cackling over shots of grandpa going face first into the lime Jell-O. "Extreme Close-Up" is television-intensive television.