Speaking Freely of ‘ Amistad’ : Even when playing historical personages, Anthony Hopkins and Morgan Freeman share a no-nonsense philosophy of acting.

Two of our best actors are giggling like a pair of seventh-graders. This was not part of the plan. The plan called for two of our best actors to pose solemnly for photographers in front of a stark, black-and-white tableau, summoning all the gravitas that their distinguished personas could muster.

After all, both Anthony Hopkins and Morgan Freeman are playing iconic American figures in “Amistad,” a significant American movie. Hopkins is John Quincy Adams; Freeman, a fictitious character named Theodore Joadson, a prominent businessman and activist in the abolitionist movement.

It therefore seemed reasonable to expect these paragons of their profession would assume the dignified mien demanded by the occasion. No way, no how. The photo session in the penthouse of a Park Avenue hotel is doomed from the moment Freeman strides into the room to embrace Hopkins like a long-lost relative.

“You don’t look like the guy I know named Anthony Hopkins,” Freeman says, embracing Hopkins.

“No, I don’t. Actually I look like John Quincy Adams,” Hopkins calls back.

“Yeah, the guy I know’s a lot shorter,” says Freeman, who looms more than a few inches above Hopkins.

More laughs. They exchange a few publicity-tour war stories before talking about the weather in Boston a year ago when they filmed scenes for “Amistad” near the State House, cast as the U.S. Capitol circa 1839-40.

“God, was it cold that day,” Hopkins says to Freeman. After the pictures, Hopkins, energized by the gratuitous silliness, settles down to talk about how it came to pass that this native of Port Talbot, Wales, is playing an American president for the second time in three years.

Hopkins had hundreds of film clips at his disposal to watch while creating his Oscar-nominated portrayal in Oliver Stone’s “Nixon.” This time he started with a two-page summary of John Quincy Adams’ life in what he recalls as a coffee-table book about the presidents. Somehow, Hopkins (who often impresses you so much you believe he could play you if given the chance) has fashioned an Adams very close to historical accounts describing him as a frail but feisty lion in winter, near-deaf, irascible, ferociously eloquent.

“I was in Mexico doing ‘Mark of Zorro’ with Antonio Banderas when Spielberg calls me and asks, ‘Think you can tackle a Boston accent?’ So I got a very good voice coach and started collecting prototypes of Boston accents, high and low. I also listened to a recording of Walt Whitman reading ‘Leaves of Grass.’ I know he’s not from Boston, but it helped me structure the sound of the character phonetically.

“So I send Spielberg a recording of me doing the voice, and he tells me, ‘It sounds great. The only problem is it sounds a little harsh. Maybe you could soften it a bit.’ So I go back to my acting coach, who asks me is there anyone I can imitate? . . . I said, ‘What about Lionel Barrymore?’ And she tells me, whatever I feel like doing. So there’s probably a little of the Barrymore you see in ‘Key Largo’ mixed in with everything else that goes with the Adams character.”

Adams was at least a real-life personage compared with Theodore Joadson, who, Freeman says as he takes his interview turn, was created as a composite mix of such African American abolitionists as David Walker, Henry Highland Garnet and, especially, James Forten, an entrepreneur and inventor. Forten even had a friendship with Robert Gould Shaw, Freeman says, the white Union Army officer who led the ill-fated black regiment immortalized in 1989’s “Glory.” Freeman co-starred as a member of the regiment in that film.

Is it difficult for Freeman to get a fix on such composite roles? He shrugs. “Nothing more complicated than learning the lines and putting on the costume. Because you’re not any different in a tie and vest than you are in a top hat and a gold-tipped cane. You may want to be careful with your diction and your accent, but really there’s no mystery to the process beyond saying the lines and letting them define who you are.”

Hopkins also endorses this no-nonsense approach to acting. “The whole tendency now is to improvise everything. . . . And maybe 30, 40 years ago this naturalistic approach, where you looked beyond the text for the character, was considered a necessary antidote to some of the excesses of the past. But now it’s gone the other way. It’s become lazy and indulgent, and I think it’s got to go back to what was told to us when we first learned Shakespeare. That if you speak the verse, you don’t have to amble around looking for subtext. You know? Just say the lines.”