SHIFTS IN THE PERCEIVED LOCATION OF A BLURRED EDGE INCREASE WITH CONTRAST

Perceived brightness is nonlinearly related to luminance. Consequently , any mechanism operating on the (transformed) luminance profile of a blurred edge to detect its location should make errors, and the magnit ude of these errors should increase with contrast. The perceived locat ion of a blurred edge was measured at a range of contrasts and a range of blur space constants in a vernier alignment task. It was found tha t the perceived location of a blurred edge was affected by the contras t and the blur space constant of the edge. At low contrasts, the appar ent location of the blurred edge was near the calculated location of t he edge, assuming the linear transduction of luminance. At higher cont rasts, the perceived location of a blurred edge was shifted toward the dark side of the edge, and the shift increased with contrast.