1. An image processing system configured to determine an intrinsic colour component of one or more objects present in a sequence of frames, for use in rendering the one or more objects, wherein some of the frames of the sequence are to be used as lighting keyframes, the image processing system comprising: lighting determination logic configured to: determine a lighting estimate for a lighting keyframe A of the sequence of frames; determine a lighting estimate for a lighting keyframe B of the sequence of frames; and determine a lighting estimate for an intermediate frame positioned between the lighting keyframes A and B in the sequence, by interpolating between the lighting estimates determined for the lighting keyframes A and B of the sequence; and intrinsic colour determination logic configured to use the determined lighting estimate for the intermediate frame to separate image values representing the one or more objects in the intermediate frame into an intrinsic colour component and a shading component, wherein the intrinsic colour component is for use in rendering the one or more objects.