Signed Pixels : advantages
	Signed pixels seem at first to be counter-intuitive but they have numerous advantages. n A value of 0 or mid grey can be viewed as the ‘most likely’ value that a pixel takes on in the absence of other information. n If you do arithmetic on images, in particular subtract one image from another, then negative values of pixels naturally arise. n Signed pixels allow straightforward implementation of contrast adjustments. For instance multiplying an image by 0.5 halves the contrast in the image.