1. An image processing system comprising: an image processing unit configured to receive two or more images of a scene acquired by an imaging assembly and to classify a first pixel group of one of the two or more images as background or foreground, wherein classification performed by the processing unit is at least partially based on a spatiotemporal deviation value (SDV), which SDV is indicative of a spatiotemporal deviation between the first pixel group and a corresponding pixel group in a different image.