Michael Fassbender and Alicia Vikander have insisted they plan to keep their relationship private to avoid turning into a "brand".
The Irish star and the Oscar-winning actress have been tight-lipped about their off-screen romance since playing husband and wife in the upcoming film The Light Between Oceans.
In a joint interview with Entertainment Weekly, Michael and Alicia appeared reluctant to discuss their love life when asked how they judged if their feelings on set were real.
Michael said: "It wasn't the first time in a movie either of us had played somebody who is falling in love.
"There is an element of separation there. If I'm playing a murderer, I don't go out and start murdering people."
Alicia added: "I think we've made a clear statement that we keep certain things just between us. It was very easy to unite, but that's quite personal."
Michael, a two-time Oscar nominee, admitted he may have been curious about actors' lives growing up but that didn't "obligate them" to reveal all.
He added: "It's the worst thing if you're sitting there in the theatre, going, 'Oh, that's the guy who dates this person and likes to do this in the morning and that in the afternoon'. Then you're just watching a brand, as opposed to an actor."
Swedish star Alicia won a Best Supporting Actress Oscar this year for her role in The Danish Girl opposite Eddie Redmayne.
The Light Between Oceans is due to be released in UK cinemas on November 4.