1. A method for motion estimation in a sequence of image data, comprising: characterizing movement of a camera or viewer, comprising a change in one or more of view direction and position, between a pair of fields or frames in a sequence of image data; determining respective sets of candidate motion vectors for positions of objects in one of the fields or frames relative to positions of the objects in the other of the fields or frames; and adjusting the sets of candidate motion vectors using the characterized movement of the camera or viewer position, the adjusting comprising at least one of (1) adjusting criteria for selecting candidate motion vectors, in dependence on the characterized movement of the camera or viewer position and (2) adjusting one or more of a direction and a magnitude of a candidate motion vector in dependence on the characterized movement of the camera or viewer position; and deriving, by motion estimation, and using the respective sets of candidate motion vectors, a set of motion vectors for describing movements of regions in the one of the fields or frames in the pair relative to the other of the fields or frames of the pair, separated from movements of those regions attributable to the characterized movement of the camera or viewer position.