Employing various quantities of makeup along the way, Leonardo DiCaprio plays the founding director of the FBI—young, old and in-between—in Clint Eastwood’s characteristically restrained, even-handed, visually elegant biography of one of the most controversial and polarizing figures in twentieth-century American history. “J. Edgar” certainly represents a tour de force for the actor, even if in the later stages of the subject’s life the prosthetics make him resemble Truman Capote more than Hoover. As to the film, it’s consistently interesting as intellectual fodder but so intent on not becoming sensationalistic that it’s rarely emotionally compelling.

That might come as a surprise given that the screenplay is by Dustin Lance Black, who wrote “Milk,” which naturally dealt very forthrightly with—indeed, celebrated—its subject’s homosexuality. There has been much recent speculation about Hoover’s sexuality, and in particular his relationship with long-time associate Clyde Tolson (played here by Armie Hammer). But the film in effect skirts the issue, opting instead to suggest that he remained closeted and repressed all his life—especially since his dominating mother (played by Judi Dench) had instilled her detestation of what she called “daffodils” in him—and that doing so might have helped engender his rage against perceived enemies (as well as his continued awkwardness around women). This cautious approach avoids turning the picture into a tabloid-quality treatment in Oliver Stone mode, but it also makes for fairly tepid going overall.

In any event, despite dealing with his relationship with Tolson and the one he had with his other most trusted aide, his secretary Helen Gandy (Naomi Watts), the thrust of the film isn’t simply, or even primarily, on Hoover’s personal life, but on his professional one. In Black’s hands the film is constructed for the most part as a sort of self-justifying memoir as Hoover, in his waning days, dictates a highly selective history of the agency he created to a series of hand-picked aides while recollecting episodes from his past that he won’t want recorded. That allows for a complex array of flashbacks that reveal him involved in law enforcement from his twenties as a low-level member of the Justice Department under successive attorneys general in the period after World War I. Selected by one of them to head the Bureau of Investigation because of his utter dedication and absolute scrupulosity, he aims to raise the organization from its relatively toothless beginnings to premier status in the country.

The narrative alludes to the FBI’s record in dealing with Depression-era gangsters and bootleggers in transforming itself into iconic status, but it presents as central to Hoover’s purpose the handling of the Lindbergh kidnapping case and the eventual apprehension and conviction of Bruno Richard Hauptmann. But as the screenplay makes clear, Hoover exaggerated his personal role in both areas to enhance his own reputation, until in the end—as Tolson suggests—he might well have come to believe his own version of history. And the picture doesn’t neglect to emphasize the power Hoover amassed over the years with his confidential files on anybody who mattered, and the way in which he used them to threaten Martin Luther King, Jr. and Bobby Kennedy, among others. (At the end, it’s made clear that Richard Nixon, who had recently been inaugurated at the time of Hoover’s death, could easily match him in nastiness and gamesmanship.)

“J. Edgar” glides through all of this personal and professional material with the quiet authority characteristic of Eastwood’s work. Like all of his films, it’s meticulously mounted and executed, with carefully composed and burnished, bronze-colored images courtesy of cinematographer Tom Stern and exquisite period detail from production designer James Murakami, art directors Patrick M. Sullivan and Greg Berry, set decorator Gary Fettis and costume designer Deborah Hopper, as well as aging makeup (for Hammer and Watts as well as DiCaprio) that’s not entirely convincing but better than most.

And DiCaprio manages to convey the range of Hoover’s emotion at all the character’s ages, from the rigidity and insecurity of his younger years to the simmering calmness of the later ones. It’s a fine performance, though one whose effect is somewhat obstructed (as Brad Pitt’s was in “Benjamin Button”) by the actor’s frequent encasement in prosthetics. Hammer adds some welcome dash and humor to the young Tolson, though he too suffers from the heavy make-up of the story’s later stages (you might confuse him with Dustin Hoffman’s Jack Crabb), recovering however in the final scene in which he reacts to the sight of his friend’s corpse; and Watts offers a controlled turn as the ever-loyal secretary, although she too is more expressive in the “earlier” scenes (speaking chronologically, rather than in running-time terms). The secondary parts are well filled, with Dench outstanding as a horrific mother figure; but whenever an immediately recognizable face (Ken Howard, Dermot Mulroney, Stephen Root, Gerald McRaney) shows up in a minor role, it tends to break the mood.

In the end, while there’s much to admire about “J. Edgar” in terms of craftsmanship and good taste, its lack of visceral impact makes for somewhat heavy going; one wishes for some deeper insight into the character than maternal smothering and repressed homosexuality. As a measured, careful biography, it possesses considerable strengths, but as drama it suffers, more than DiCaprio’s previous foray into such similar as Howard Hughes in “The Aviator,” from a lack of—no pun intended—penetration. In the case of such potentially lurid material, sometimes moderation—to quote Barry Goldwater—is no virtue.