Hollywood star Bradley Cooper went through a five-hour makeup process to transform into Leonard Bernstein in 'Maestro'.

The 48-year-old actor both plays the lead role and directs the new biopic about the celebrated composer and the Oscar-winning makeup artist Kazu Hiro revealed how he and his team would spend all night applying the cosmetics so he could be behind the camera in character, reports aceshowbiz.com.?

"The last stage, he had covered pretty much everywhere, the bodysuit and arms. That took over five hours. The last stage, the whole time, our call time was 1 in the morning," Hiro told an audience at the picture's New York Film Festival screening on October 2.

"The other thing was he wanted makeup to be finished before the crew call, so he would appear as Lenny to set up the shoot and everything. That also kind of made our call time two hours earlier than normal, so that was quite tough."

Hiro explained that the length of time Bradley spent in the makeup chair varied as they filmed scenes from across Bernstein's life.

He said: "(We had to) keep adding because as he gets older, we had to add more elements. The younger stage was the nose and lips and chin and a wig. After the third stage, he started having cheek and neck (additions)."

Hiro's work sparked outcry as Cooper decided to wear a prosthetic nose in his portrayal of Bernstein, who was Jewish, and the makeup artist did not intend to cause offence.

He said, "I wasn't expecting that to happen. I feel sorry that I hurt some people's feelings. My goal was and Bradley's goal was to portray Lenny as authentic as possible. Lenny had a really iconic look that everybody knows - there's so many pictures out there because he's photogenic, too - such a great person and also inspired so many people."

"So we wanted to respect the look too, on the inside. So that's why we did several different tests and went through lots of decisions and that was the outcome in the movie."