Steve Martin admits that he originally wanted Tom Hanks to play the role of Ray Porter, a character he pretty much gave birth to through his bestselling novella and his own screenplay adaptation. But he takes on the role with such finesse that he reminds us that he’s one of the great actors of our time.

Martin also takes his professionalism into the junkets, where he speaks astounding thoughtfulness and articulacy. Below, Martin talks about bringing to life “Shopgirl,” a story about a regular girl (Claire Danes) who is trapped emotionally in love between the affections of a rich middle aged man (Martin) and a sweet, bumbling boy (Jason Schwartzman).

Q: Steve, given that you wrote the book and the screenplay, how did you navigate the relationship with director Anand Tucker and his own vision for the movie? Did you have any disagreements?

STEVE: I just did. He’s a very gentle guy. He understood the script for the movie. There was never any contention while we were shooting, so it was fine.

Q: Did you ever think of directing it yourself?

STEVE: No, not really. I have never directed.

Q: How do you decide a work of writing is a film or a book?

STEVE: That usually comes in a framework in your brain. You know that it’s sentence oriented or visual. You just know somehow.

Q: Did you always want to play the part of Ray or did you consider another actor?

STEVE: I suspected it. The first person I asked was Tom Hanks. I thought he was really the perfect guy to play it.

Q: So why was Claire cast for the part?

STEVE: As soon as we had lunch, Claire didn’t have to speak before we knew she was exactly right for it. Claire is naturally beautiful as opposed to unnaturally beautiful in Hollywood. Claire just fit with her simplicity into this role. She had a quiet solitude, which we’ve seen before. There was something about the simplicity of Claire’s performance that was amazing.

Q: We never understand why Ray was having trouble with loving somebody. Did you ever come up with an explanation through a backstory?

STEVE: You know, I cringe at backstory, because it never quite explains [things], or it gets into some psychological thing that is never quite right and never quite the truth. Who knows why someone is some way? You can’t just say, “And Ray’s dad never loved him.” It doesn’t explain it. Yet we all know there are people like that, and we meet them and deal with them, and are them, and it’s never quite explained. But you never ask how can that person exist.

Q: Is “Shopgirl” autobiographical at all? You did write it and one of the things people say is that you always write a part of yourself…

STEVE: But then, your argument applies to the autobiographical side to Mirabelle since I wrote her too. Everything is culled from every source: my life, other people’s lives. I’m 60, and I’ve had sex since I was 18. There’s a lot of stuff going on. So there’s a lot of experience, whether it’s my own or somebody else’s. I wrote a book subsequently about a guy who was agoraphobic. It doesn’t apply to me at all, but I can imagine it.

Q: Why do you think Hollywood tries not to do smart romantic movies like this one?

STEVE: Good question. I always feel like there’s the person with the inspiration and then there’s the person who’s going, “No no, this other movie had this, so we have to have this.” It just starts getting wrenched out of its own heart. Our movie didn’t get wrenched. Basically, the book is about small moments and the movie is about small moments – which are the biggest.

Q: You’ve done broader comedies recently, like “Bringing Down the House” and “Cheaper By the Dozen” but you’re doing more cerebral films now. How do you go about making those choices?

STEVE: You’re implying that the choice is some kind of choice; that it’s deliberate. It’s not. It’s about where you’re going, where you’re headed. Is it ready to go? Do I like it? Who’s in it? There are a million different things. There’s no “star chamber” somewhere trying to figure out the next move. I’m sure it works in some cases, but it doesn’t work for me.

Q: How do you judge if a film is a success?

STEVE: Whether I’m involved in creating it or something, as a personal issue later, do I respect that thing, you only know that five or ten years later? The most immediate thing is, how is it received? You want it to happen. I don’t know anybody who says, unless you’re making excuses, “Yeah, it’s an art thing, they’re too stupid to get it, I’m confident even though it stiffed.”

Q: Do you have a more parental feeling with something like this that you’ve created?

STEVE: No. I was having a discussion with a friend years ago about psychiatry. They were comparing psychiatry to art and saying that being in psychotherapy was an artistic process. He said that there was a big difference between psychiatry and being an artist is that as an artist, you abandon what is made. In psychiatry, you try to retain your thoughts and feelings. That’s essentially what I do. Once it’s done it’s an accident if I see it again. Sometimes it’s a happy accident, sometimes it’s not.

"Shopgirl" opens in theaters this Friday.