After the highly anticipated casting for the film adaptation of "Fifty Shades of Grey", fans of the erotica novel now have other things in mind. Exactly how much sex involving Charlie Hunnam and Dakota Johnson will be in the film? Readers of the trilogy written by E.L. James know that every scene is filled with S&M sex. How would this be shown on the big screen?

What had started off as "Twilight"-inspired fan fiction, "Fifty Shades of Grey" is now the world's best-selling paperback beating the likes of "Harry Potter" by J.K. Rowling. The book certainly has magic all on its' own. Given the S&M involved in the novels, how would director Sam Taylor-Johnson transition that for the movie?

"She is going to have to walk a very fine line," states Editor of Women and Hollywood blog on Indiewire Melissa Silverstein, adding, "That's the $1,000 question. Are they going to push things to a different level?"

Producers of the film did make it clear to the fans that the film will still be R-rated but won't push the sexual content to NC-17 by the Motion Picture Association of America.

"Historically, the NC-17 rating has dramatically impacted box office. It's the kiss of death in most cases," explains Kirby Dick, director of "This Film Is Not Yet Rated."

Of course, the film version might be different for the "uncut DVD release." Director of "Twilight", Catherine Hardwicke explains that the sex onscreen might be a bit uncomfortable so producers of the film will certainly have to rely on DVD releases for the raunchy scenes.

"People were surprised to see something so sexual," said Hardwicke, adding, "I thought after the success of (the novel) Fifty Shades of Grey that people would be totally excited to see it. But it was too intense. It's a whole different feeling on the screen."

"In the end, people are still uptight and nervous about sexuality in movies," continues Catherine.

In summary, Charlie Hunnam and Dakota Johnson have their work cut out for them but chances are the sex scenes won't be as steamy as the ones described in the book.