Jessica Alba's has undergone a dramatic makeunder for her new movie role.

The actress - who is better known for steaming up the big screen in films such as the Fantastic Four and Into The Blue - was almost unrecognisable as she filmed scenes for An Invisible Sign of My Own yesterday.

A bare-faced Jess looked serious at she strode along purposely wearing a sleeping bag-like puffa coat with her hair in pigtails.

Her Ugly Betty-inspired look is for her role as a mathematical genius who gets a serious illness which causes her to lose the will to live.

But Jess' character learns to cope with her circumstances by teaching maths to children.

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