Some machines are able to deal with small-sized fitting in real-time [15,16]. It is possible to track faces in a video (frame rate should then typically be 24 frames/second and 15 at the minimum), but the resolution catered for is often relatively low (less than 100x100 pixel). Applications that respond so quickly were made far more practical owing to a multi-resolution (multi-scale) approach. In order to decrease the total run-time, varying increasing image resolutions become available for selection at each search iteration. Finer resolution images are usually used at the later stages of the search, whereas low-resolution (coarse) ones at the very start. Since the similarity between the model and the target is poor at the start, the resolution (and hence the scale of the objects) will have little effect on the fitting. Some visual examples of AAM search are shown in .