Watch: Colin Firth Was 'Undecided for a Bit' about Playing Gay in 'Supernova'

Although he had already played a gay character in a film - starring in Tom Ford's 2009 movie adaptation of Christopher Isherwood's 1964 novel "A Single Man" - heterosexual actor Colin Firth admitted to having been "undecided for a bit" when it came to signing on to Harry Macqueen's drama "Supernova," in which he plays one half of a longtime same-sex couple.

Firth and "Supernova" co-star Stanley Tucci - also heterosexual, and who also has portrayed LGBTQ characters in the past - both spoke with Yahoo! Movies about the film, in which Tucci plays a novelist suffering from early onset dementia and Firth plays his husband, a concert pianist.

The conversation has changed since 2009 and "A Single Man." As Yahoo! Movies noted, "in recent years the casting of straight performers in LGBTQ roles has become a more contested issue."

Firth indicated he was cognizant of this, telling Yahoo! Movies, "This was a discussion, and it was a very serious one."

The actor, who was nominated for an Oscar for his work in "A Single Man," went on to say that whether a character is LGBTQ or not, "Taking on a role feels like an insufferable presumption. You know nothing about this person's lived experience, and yet you are presuming to take a step into it and convince everybody that this is a deeply felt experience."

That "presumption," Firth added, "feels outrageous," but at the same time, he noted, "it's also the job.

"So I feel like we are then challenged to really explore this with as much sensitivity and integrity and honesty, and make it as personal as you possibly can. Then you just hope it resonates in a way that is somewhat truthful."

Tucci had appeared earlier in an interview with the CBS talk show Sunday Morning, in which he said he had "difficulty" with the idea of straight actors being shut out of LGBTQ roles. "I think that acting is all about not being yourself," Tucci said in that interview. "If we were to use that as a template, then we would only ever play ourselves."

But Tucci went on to say he was sympathetic with LGTBQ actors: "I think what we need to do, we need to give more gay actors opportunities.

"People who are gay have only recently, in the last few years really, have been able to say, 'I'm gay and I'm an actor and I can play straight roles,' " Tucci noted. "They always had to hide their sexuality so that they could play the leading man or leading woman."

Tucci reiterated some of his earlier thoughts in the Yahoo! Movies interview, including the suggestion that the film's message is universal. Praising Macqueen's script, Tucci said it "didn't matter if it was a gay relationship or a straight relationship. It was just about love and loss."

To see the Yahoo! Movies interview with Firth and Tucci, follow this link.