For Amitabh Bachchan "Black" is the crowning glory of his acting career. In director Sanjay Leela Bhansali's film the superstar plays a teacher to the physically challenged heroine portrayed by Rani Mukherjee.

Bhansali's film is a celebration of a deaf, dumb and blind girl's struggle to lead a normal life. Bachchan, who plays Rani's teacher, friend and guide, said: "There is not a single scene in 'Black' that I have done before".

Bachchan and Rani were in Delhi Monday night to promote their latest film.

Ecstatic about the film's prospects, Bachchan said: "The film will take Indian cinema several notches higher. It was enormously rewarding to work in it."

For Rani too, Bhansali's film is a career milestone. Initially, the actress was unsure about being a part of Bhansali's project.

"But when the script was narrated to me, I knew I would be doing the film. It was a most enriching experience," said Rani, who is better known for her romantic roles.

In "Black" Rani's character is trapped in a world of darkness that is penetrated neither by sound nor by light. But with the help of her teacher she finds her way to a unique understanding of the physical world.

"Black" shows how the teacher and his disabled pupil communicate through a vocabulary of their own: the language of touch. They inscribe alphabets on their palms.

Bhansali's film promises to create a new genre of socially committed films that blend the best of both art and mainstream cinema.

Bachchan tells: "'Black' has all the ingredients of mainstream cinema, but it's able to get across this message powerfully to the audience. The film shows if you are determined, you can achieve anything."

To act in such an intense and original film was a transformative experience for both Bachchan and Rani.

Bachchan said: "It was an extremely uplifting experience. It took me six months of training to prepare for the movie. It has turned out to be the most challenging film of my career.

"If you delve deeper into the lives of the physically challenged, you will find in them a hunger to live life to the full.

"Their continuous struggle and their joys make you feel small. Their desire to completely experience life is deeply inspiring."

Acting in the film has clearly pushed the envelope for Bachchan, who is known for his astonishing versatility. He appears to be engaged in a relentless reinvention of himself as an artist and a human being.

The legendary actor seems to be bursting with creative energy at an age when his contemporaries prefer to live a quiet life. "Once an artist is satisfied, he is finished," said Bachchan.