Ryan Reynolds used to observe "old master" Denzel Washington on the set of Safe House.

Ryan has been open about his admiration for the veteran actor and used to study his idol's thespian skills when they were shooting together, director Daniel Espinosa has revealed.

Daniel said that Ryan and Denzel's onscreen relationship was mirrored in real life.

In Safe House, Ryan portrays a young CIA agent tasked to look after a fugitive played by Denzel - in a safe house. But following an attack the pair find themselves on the run together.

"I would be shooting a scene with Denzel and see Ryan off camera, watching this old master working his craft," Daniel told fashion website Mr. Porter. "It was almost as if their experience was the same off screen as on."

The filmmaker also spoke about his relationship with Denzel.

Daniel wanted to earn the Hollywood icon's respect and hoped to work with him as an equal.

But he admitted that filming wasn't always a smooth process and the pair ended up rowing regularly.

However, the difficulties of the experience created a bond between them.

"I thought, if I can sit down with Denzel, then in the end he will be a human being, as will I," he said. "If I couldn't earn his respect at that point then I was not worthy of directing him. We got into lots of fights and arguments and talks... and managed to create a brotherhood so that when we went to war, we went to war together."