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 the 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; wherein the 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 comprises defining the candidate motion vectors as respective sums of a vector derived from the characterized movement of the camera or viewer at a location to which that candidate motion vector applies and a respective vector representing an estimated true motion of a respective object at the location to which the candidate motion vector applies, and further comprising storing the vector representing an estimated true motion of an object and using that stored vector in at least one of the sets of candidate vectors for object motion, the at least one of the sets pertaining to one or more locations neighboring the location to which that candidate motion vector applies, in the one of the fields or frames.