The 27-year-old actress said in the February issue of Vogue that filming Fifty Shades Darker with Dornan was an uninhibited but "very trusting" experience.
"Nudity is really interesting for an actor," Johnson admitted. "Jamie and I worked so incredibly closely for so long. There were no inhibitions, and it was very honest, very trusting. But I mean, what a gamble! What if he had turned out to be a total [expletive]?"
"There's no makeup. There are no clothes to tell you a bit about the story. There's no jewelry to give you a clue about social status. So it becomes purely about the performance," she added of the steamy scenes.
The Fifty Shades movies are based on the erotic book trilogy of the same name by E.L. James. Dornan had shared similar sentiments about working with Johnson in an interview with Good Morning America in August.
"We have a lot of fun together," he said. "Dakota's funny. We've been through this mad journey together. I'm very thankful that I've done it with someone who's easy to do it with, because it could've been a very different experience had we not got on."
The Fifty Shades series follows the romance between Anastasia Steele (Johnson), an inexperienced college student, and Christian Grey (Dornan) a BDSM-loving businessman. Fifty Shades Darker will be rated R for "strong erotic sexual content, some graphic nudity and language."
"There are some very chic avenues in BDSM," Johnson told Vogue. "It can be very beautiful and tasteful, and the materials can be luxurious. It's not like being on Hollywood Boulevard and walking by a ball-gag store."
"What I admire is the bravery and the honesty of people who get down with it, who aren't afraid to say that they need something a bit more in order to get off. America is still so sexually oppressed. Isn't God's gift to humans the orgasm?" she said.
Fifty Shades Darker opens in theaters Feb. 10. The movie was preceded by Fifty Shades of Grey, which opened in 2015, and will be followed by Fifty Shades Freed, which opens in 2018.