The light intensity values of a first and second image are stored in a memory as pixels. A transformation from the second image to a derived image is perforated by a spline function in cooperation with a spline control grid. The spline control grid has a plurality of control vertices at predetermined locations with respect to the pixels of the second image. The transformation adjusts the light intensity values proportional to the distance between the control vertices and the pixels of the second image. The first image is compared with the derived image. The difference between the first image and the derived image is determined. The control vertices of the control grid are iteratively displaced until the difference between the first and derived image is less than a desired amount. The final coordinates of the control vertices parametrize the motion field of the first and second image.