Johnson plays Ana Steele, the protagonist of the film trilogy, which releases its third and final chapter – Fifty Shades Freed – next year.
Speaking in a behind-the-scenes featurette shared by Celebuzz, Foley said: “She’s so intelligent. You can’t get things past her.
“You can’t ask her to do something with a bulls**t reason.”
He recalled: “She was relentless in her pursuit of making this character as real and believable as she could possibly be.
“Each time she made a decision to do something, you felt, ‘OK, yeah, that’s what Anna would do’.
“And if I try to get her to do something Anna wouldn’t do, she let me know and we didn’t do it.”
It seems that Johnson was so hands-on with the process on set that Foley wouldn’t rule out a career for her behind the camera.
“She knows exactly what the camera’s doing and what it’s seeing,” he admitted.
“If she wanted to, she could be a really good director. SHe’s got a sense of the whole, which is unusual for an actor.”
The Fifty Shades Darker Blu-ray and DVD has already been a storming success in the US, as it rocketed to No1.
A UK release follows next month.
Fifty Shades Darker is available on Digital HD from 12th June and on Blu-ray™ and DVD from 26th June 2017, from Universal Pictures (UK).