May 7, 2015 9:30 AM EDT

When you think of Fifty Shades of Grey, you’re probably more likely to think about how the characters get undressed than what they’re wearing onscreen. But the movie’s costumes are indeed an important part of telling the story, as designer Mark Bridges explains in this behind-the-scenes clip.

Dakota Johnson says Anastasia has “no fashion sense” at the beginning of the film. But as the plot progresses, her clothes become more refined. Readers of the book were going to expect something special for the grey dress she wears at her graduation, so Bridges pays particular attention to that silk chiffon number.

Fifty Shades of Grey is out now on Digital HD; it arrives on DVD and Blu-Ray May 8.

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