1. A method of image processing comprising the steps of: calculating a difference measure of a difference in pixel values between corresponding blocks of a current image field and an adjacent image field; calculating a variability measure of a variability of pixel values in respect of at least one of said corresponding blocks; determining whether the difference measure exceeds the variability measure; and if the difference measure exceeds the variability measure, setting respective inter-image mixing values for pixels in the corresponding block of the current image field to indicate that the current image field should be mixed with the adjacent image field at that pixel position to at most a predetermined extent.