Perceptual scales for chromatic and luminance blur in noise textures

We have measured the relative perceptual scales for chromatic and luminance blur in dense textures comprised of color and luminance Gabors, using a modification of the method of paired comparisons. We find that the rate at which perceived blur grows with physical blur, when normalized to 1.0 for luminance, is 0.2 for red-green and 0.06 for blue-yellow blur. It is argued that the relatively severely compressed perceptual scales for red-green and blue-yellow blur are a contributary factor to the observation that when the color but not luminance layer of an image of a natural scene is blurred, there is little or no impression of blur (Wandell, 1995).