In an image display apparatus, a video signal is divided for each field into a plurality of sub-fields, each of which is weighted according to the duration of time or number of pulses. The plurality of sub-fields are temporally superimposed for display, so that a grayscale representation is provided. A video signal for the current field is delayed by one field, and output as a video signal for the previous field. Based on the video signal for the current field and the video signal for the previous field, a luminance gradient of an image is detected. A difference between the video signal for the current field and the video signal for the previous field is calculated. Based on the calculated difference and the detected gradient, the amount of motion of the image is calculated by a detecting circuit. Based on the calculated amount of motion of the image, dynamic false contours are reduced by an image data processing circuit.