High pass filters are zero sum, they do not change the average brightness or color of the combined image. Instead they shift energy from neighboring sub-pixels to allow high spatial frequency luminance modulation in the other channels to be expressed by each sub-pixel, regardless of color. These zero sum filters serve to sharpen the image back to original image sharpness. Thus the high spatial frequency luminance information is represented at the individual sub-pixel level, while the chrominance signal is low pass filtered to be expressed over a neighborhood of sub-pixels of all the color primararies.