It's hard to recognise Beyoncé under this retro wig. The R&B superstar covered up her long tresses in a Fifties bouffant, switching from light brown to blonde in the process.

Go-Etta: Beyoncé as Etta James

The change in image is part of her transformation into legendary blues singer Etta James.

Beyoncé stepped into James's shoes for the Hollywood film Cadillac Records, of which she is also an executive producer. The film charts the life of Chicago-based record company executive Leonard Chess, played by Oscar winner Adrien Brody.

Chess mates: Beyoncé with Adrien Brody

With his brother Phil, Leonard ran Chess Records throughout the Fifties and Sixties, where the star-studded roster included James, Bo Diddley, Muddy Waters, Chuck Berry and Little Walter.

It is the first acting role for Beyoncé since her turn as Deena Jones in the mus ical smash hi t Dreamgi rl s, which earned her two Golden Globe nominations, for best actress and best original song.

Beyoncé, who played a character loosely based on Diana Ross in Dreamgirls, has big shoes to fill as the real- life Etta James.

The gutsy, full-figured singer belted out many standout blues and jazz tracks, including At Last, for which she was inducted into the Grammy Hall of Fame in 1999.

The casting of slender Beyoncé in the role has raised a few eyebrows, not least from 70-year-old James herself.

She said: "It's a privilege and an honour to have somebody like that girl. I don't think she looks like me, but that's all right. They can fix that up."