1. A method of combining multiple images wherein the images exhibit variations in illumination between one another, the method comprising: generating a plurality of images of the same portion of an object, each image being represented by a respective set of image data; applying a comparative data transform to each set of image data such that the transformed comparative image data isolates and preserves variations in the illumination between the plurality of images; determining at least one normalisation transform from the transformed comparative image data sets such that when applied to at least one of the plurality of image data sets minimises the variation in illumination between the plurality of image data sets; applying the or each determined normalisation transform to the or each respective set of image data; and transforming the normalised sets of image data to a single image of the portion of the object.