1. A method of interpolating a new image within an existing sequence of related images using motion vectors applicable to pixels of an image in the said existing sequence, where the pixels of at least one existing image adjacent to the new image contribute to the new image, and the positions of the said contributions in the new image depend on scaled motion vectors applicable to respective contributing pixels, characterised in that: two or more motion vectors are derived for a region of an existing image comprising at least two pixels; the derived vectors are used to create respective shifted versions of the said existing image region; and, the shifted regions are combined in a weighted sum to form a new image where the weight depends on a probability of accuracy measure for the respective vector that depends on a comparison of existing images.