With their electric colors and abbreviated hemlines, the Spring clothes that Jason Wu showed last September sent a clear message: Grateful as he was for the attention he received after Michelle Obama wore his gown on inauguration night, he didn't want to become recognized for just one kind of look. Now, for Fall, he seems determined to move even further from the princess dresses that were his first claim to fame. If the results were occasionally uneven, you can't fault the 27-year-old designer's impulse to expand the scope of what he's known for.

"There's a big menswear message and a big outerwear message," he said a couple of days before his show. The starting point for his short-sleeve jackets, oversize cashmere coats, boxy mohair sweaters, and fold-over trousers was Irving Penn—the man himself, not his works. Plaid jackets and crisp white shirts were the late photographer's daily uniform. Here, they had an appealing, shrugged-on sensibility that suggests Wu has noticed the movement elsewhere in fashion toward clean, spare classics.

Penn's photographs were also an influence, as it turned out, evident in some of the collection's key prints. Those aren't polka dots on that strapless shantung bubble dress, they're a reproduction of a cigarette-burn print. Cast-off negatives of chemical spills, meanwhile, inspired the gold leafing on Wu's duchesse satin sheaths. It didn't all work: Some experiments in eveningwear, namely a pair of black hand-draped Chantilly lace dresses, lacked the effervescent quality of Wu's best designs. But he was back to form with an off-the-shoulder dress with pheasant feathers trapped between layers of tulle, as well as an almost weightless plume-print silk tulle strapless style. It's a pity the West Chelsea venue wasn't better lit to allow a closer look.