The Enneads

A geometric test pattern serves as a calibration target for photographic reproduction. The main design sits within a rectangular frame. At the center, a large circle consists of multiple concentric rings with a crosshair. Four diagonal lines originate from the corners of the outer frame and meet at the center point. Each corner of the frame contains a set of concentric quarter-circles. At the top, bottom, left, and right midpoints, triangular and diamond-shaped regions contain closely spaced parallel lines of varying orientations. A horizontal scale with tick marks numbered from 0 to 10 appears near the bottom center inside the frame.