A method (100) is disclosed of classifying elements in a region within a frame (410). The method (100) creates (145) a background model (150) of at least said region based on a statistical function applied to features of elements of said region in a set of frames. A mapping (130) of features to labels is also received. A difference measure comprising a plurality of difference values is then calculated based on features of elements in the region and features of the background model (150). The method (100) then classifies (180) elements based upon the difference measure and the mapping (130).