James Franco has admitted he felt everything in 127 Hours depended on the scene in which he appears to cut off his own arm.
The actor stars in Danny Boyle's new film which tells the true story of when adventurer Aron Ralston had to amputate his own arm after getting stuck rockclimbing.
James said: "We knew this would be the scene that everybody would be anticipating anxiously but also kind of wanting to see.
"It was a balancing act. It was finding the middle road between showing too much and not showing enough and shortchanging the story and the experience."
He went on: "That act was like a portal for Aron to go through, and the audience, to have the full experience, needs to go through that portal with him."
Aron was trapped with his arm stuck under a fallen boulder in a Utah canyon for six days with little food and water, before he finally managed to find the energy to cut off his arm.
During the time he was stranded he used a video camera to record farewell messages to his family, which James has watched and recreated in the film.
He said: "What was so powerful about the real messages was the dignity with which he held himself together. He thought he was going to die and thought these would be the last things his family, his mother, would ever see, and so he wanted to leave these dignified and heartfelt messages, rather than messages full of self-pity."
:: 127 Hours is released in January