Disclosed is an apparatus for forming a composite image of a scene from a plurality of overlapping elemental images, the apparatus comprising: a selector for selecting one point in one of the plurality of images and another point in a second one of the plurality of images, the first point and the other point being overlaid in the composite image and being of substantially the same point in the scene; a determiner for determining, when the first point and the other point are overlaid, the gradient across the overlap between the first and other elementary image; and an adjuster for adjusting one of the first and second elementary image to minimize the gradient across the overlap. A corresponding method is also disclosed.