The answer is that it depends on the director. For David Fincher or the Coen brothers, having this level of exactitude and precision is what their craft is all

The answer is that it depends on the director. For David Fincher or the Coen brothers, having this level of exactitude and precision is what their craft is all about. But for plenty of other masters - think Cassavetes, Mike Leigh, even PTA - the actor's outstanding talent and instincts bring something to the script and vision that is outside of their prescriptive powers. Their focus is essentially setting up a framework for magic to happen inside of.