British actress Keira Knightley has turned her back on major Hollywood roles - because they do not challenge her emotionally. The Atonement star, 22, says she "cannot imagine" doing another big-budget Pirates Of The Caribbean-style movie. Instead she wants to concentrate on quirky small-budget films which stretch her acting skills. She says, "I can't imagine ever doing another one. I had five months off from Pirates during the summer last year, when I made Silk and Atonement, and it was so great - I want to be able to explore emotions in smaller projects. "That's not to say I won't suddenly read a big Hollywood blockbuster and go 'oooh, that might be good...' But I haven't yet."