An image rendering method the steps of, for a view of a virtual model having a locus of interest, performing flexible scale rasterisation with a first bin distribution for a luminance channel, and mapping the results to a first pixel space; performing flexible scale rasterisation with a second bin distribution for chrominance channels, and mapping the results to a second pixel space; and outputting an image based upon the luminance and chrominance results mapped to the first and second pixel spaces; where the second bin distribution includes larger bins than the first bin distribution in a region outside the locus of interest.