Image sequence analysis has been an active research area for many years. It brought new insights into a lot of distinct applications, ranging from site securing (intrusion detection) to image coding and video indexing as well as path determination or object handling in robotics. The pioneering contributions provided in the 1980s (e.g., the works of Hildreth, Nagel, and Horn and Schunck) aimed at two-dimensional (2-D) image sequence analysis through motion field estimation have benefited from major technological and methodological advances. New capabilities in capturing three-dimensional scenes have opened the road for emerging applications and have therefore led to more demanding solutions for object feature extraction, reconstruction, and interpretation. This column revisits some up-to-date problems in digital imaging. A future column will point out some of the challenges that should be considered in medical imaging. Topics covered include motion estimation; motion based image segmentation; and tracking.