Billock, Cunningham & Tsou (2008) 2 APPROVED FOR PUBLIC RELEASEIntroduction Discrimination tasks in combat target identification are legion. For example, operators need to discriminate a target against a background and to discriminate a set of similar targets from one another. The first task is a necessary, but not sufficient condition for targeting, while the second task is essential to solve decoy and friendly-fire problems. Both tasks are complicated by camouflage. If it were necessary to consider the set of all possible targets, backgrounds and camouflage, the combinatorial problem would be disheartening. However, a consideration of visual psychophysics, image science and fractal mathematics suggests that a particularly simple optical signature provides a low-dimensional solution. Figure 1. An Expeditionary Fighting Vehicle (General Dynamics, Inc. ) concealed against foliage with two different camouflage schemes. The rear of the vehicle is in standard single-scale NATO camouflage and pops-out from the foliage background. The front of the vehicle (see figure bottom) is concealed by a two-scale MARPAT camouflage pattern and is less conspicuous (O'Neill et al., 2004). If the number of scales increases, the perception of fractal-like camouflage is less distance dependent. Courtesy of the United States Marine Corps Systems Command. Background: Perceptual Popout, Fractals and Camouflage It is well known that humans effortlessly (and preattentively) discriminate images which differ significantly in their second-order statistics (the so-called "pop-out" phenomenon), while images