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