Director Scott Cooper is impressed with Johnny Depp's work ethic.

The American filmmaker is working with the 50-year-old actor on the Whitey Bulger biopic 'Black Mass', and was thrilled that Depp has a ''strong point of view'' and is keen to get to set to begin filming.

Talking to, he said: ''I only want to work with actors to have a strong point of view and who want to race to set.

''And Johnny is that type of actor. He is a consummate actor. He's always pushing himself and always playing something different. He's one of the best actors in American screen history.''

Cooper hopes the film will portray Depp in a way which he's not been seen before.

He added: ''Our hope is to really craft a full-bodied portrait in ways that you haven't seen. It's exciting to see an actor like Johnny really attracted to a part like this because you've never seen him like this.''

'Black Mass' is based on the notorious Boston gangster who was arrested in 2011 in Santa Monica, California and is currently incarcerated at the United States Penitentiary in Tucson, Arizona.

He was sentenced to two consecutive life terms plus five years after he was found to have been involved in 11 murders among other crimes.