Rehearsals for his Sydney Theatre Company directorial debut are clearly weighing heavily on the mind of the Academy Award-winning "actor's actor" Philip Seymour Hoffman.

Since arriving in Sydney three weeks ago Hoffman has managed to maintain a profile so low he has barely registered a blip on the Sydney celebrity radar. That was until PS's snapper caught up with him on Thursday.

Hoffman was clearly not in the mood for posing for any pesky photographers, having been sprung having a coffee with his leading man Hugo Weaving at the Sydney Theatre Company.

Hoffman is in town on the invitation of the soon-to-be STC co-artistic directors Cate Blanchett and her playwright husband Andrew Upton to direct the latter's new play, Riflemind.

The play makes its debut in just under a month, with Weaving playing an ageing rock star. PS hears rehearsals have been intense. Upton has been spending hours at the theatre with Hoffman while Blanchett travels the globe promoting her two latest triumphs - the Bob Dylan biopic I'm Not There and her Elizabeth sequel, Golden Age.

Hoffman did open up a little to ABC radio this week, explaining that his first love as an actor was the theatre. "I got into acting for theatre. My agent kept sending me to auditions for films, and that satisfied me too. But to do them both is very important".

He said the play was about the impact of fame on young lives. "I don't think I would have been able to handle what I'm doing now in my 20s. You get to meet a lot of people and travel to a lot of great places, and those are things that I have a lot of gratitude for. But there's also a lot of pressure and weirdness."