Saint Laurent Gaspard Ulliel, Jérémie Renier, Louis Garrel. Directed by Bertrand Bonello. Rated R. Opens Friday.

Anyone interested in the life of legendary fashion designer Yves Saint Laurent probably won’t get much out of Bertrand Bonello’s impressionistic biopic Saint Laurent, which is heavy on dreamy imagery and light on facts and insights. It takes place mostly during a 10-year period in the 1960s and ’70s when Saint Laurent (Gaspard Ulliel) was at the height of his success, designing clothes that set the standard for both haute couture and everyday wear.

Not surprisingly, the costumes and sets in the movie look great, and Bonello focuses on those as Saint Laurent descends into a predictable morass of drugs, alcohol and orgies (yes, actual orgies). But the movie does little to indicate why Saint Laurent was such an artistic genius, or to delve meaningfully into his relationships, and at two and a half hours, it wears out its welcome long before it ends. One thing Saint Laurent succeeded at was bringing substance to style, but the movie about him seems to forget that part.