What an odd and provocative coincidence that black women - hardly a demographic over-represented in mainstream cinema - should be at the centre of two high-profile American films opening this week. One is The Princess and the Frog, also reviewed today on theartsdesk. The other is the multi-award-winning Precious. In the former, the princess is a brunette edition of Disney's pretty Barbie prototype. Near the beginning of Precious, by contrast, when you first spy this sullen, seriously obese figure waddling into view, you might be forgiven for asking, "Do I really want to spend 110 minutes in this character's company?" The answer is not a foregone conclusion.