Geoffrey Rush won an Oscar from his first Oscar nomination for portraying Schizophrenic Pianist David Helfgott.
Rush actually is not in the film all that much a very good portion of it focuses on the two actors playing the youngest, and younger Helfgott. It only shows briefly at the beginning, but eventually catches up with him again at the very end. This is an "acting" performance most certainly. It is all about mannerisms, and voice to show Helfgott's schizophrenia. Rush does a fine job showing the schizophrenia it is fairly realistic. I compared him to the real Helfgott, and I must say that he was pretty close to the real thing. He was not exact, but he was pretty close.
He does a good job since he is realistic without being over the top. The only problem I have with performance like these, is the actor just finds the right mannerisms, and tone but then call it a day. Which makes sense since most people with mental conditions do not really change in normal situations. Rush most of the time just keep doing the same mannerisms over and over again which are correct and he does it well. It is completely correct for the character, and for the film too, therefore I do not have a problem that he does this. Also when he does have a few chances to show a little more like his scene where he meets his father, or his reaction at the end of his comeback concert. Both scenes are very well handled and are made effective by Rush. But on the other coin his final scene he makes his mannerism sort of go away kind of oddly briefly, which is feels very false and the worst moment in his performance. Still overall he gives a good performance in a limited type of performance and tries to add more when he has the chance.