[Iris Alantiel]

I think the power of the Ring was demonstrated clearly enough in the book in the instances where it that it doesn't have to completely overpower every character. It doesn't have to affect every single character with an insane desire to possess it in order to be a powerful agent of corruption.

It makes sense that the Ring would affect different kinds of people in different ways. It's probably a pretty good test of one's character to see how they react to the Ring. By the point in the story where we meet Faramir, we already know that the Ring is powerful and corrupting. Tolkien chooses to make this a time for us to get to know a bit about Faramir's character through his actions.