1. A computer-implemented process for transferring an expression from a face in a first image to a second face in a second image, comprising using a computer to perform the following process actions: inputting a first image depicting a face without expression, a second image depicting the same face as in the first image with an expression whose details are to be transferred, and a third image depicting a face of different from the first face without expression; aligning the faces in the first, second and third images, thereby creating a correspondence between pixels in the first, second and third aligned images; for each corresponding pixel in the first and second image, computing an expression ratio image by dividing the intensity of the face with expression in the second aligned image by the intensity of the face without expression in the first aligned image; and creating a new image of a face with expression by multiplying the expression ratio image by each corresponding pixel in the third image.