Distinguishing shadows from surface boundaries using local achromatic cues
Fig 2
Contrast statistics measured from shadow and occlusion edges (N = 2000 of each category).
Green curves/symbols indicate occlusions, Magenta curves/symbols indicate shadows. (a) Distributions of Michelson contrast (left) and RMS contrast (right) for our shadow database and two sets of occlusions (oset-1: top, oset-2: bottom). Note that for both occlusion sets, the highest and lowest contrast edges are occlusions. (b) Two-dimensional scatterplot of contrast measurements for shadow and occlusion edges for both sets of occlusions. (c) Probability distribution of stimulus power πh in the high spatial frequency (>10 cycles/image) range for our shadow database (magenta curves) and both occlusion sets (green curves). (d) Rotational average of the amplitude spectrum for shadows (magenta curves) and both occlusion sets (green curves). (e) Scatterplots of πh and Michelson contrast cM for shadows (magenta symbols) and both occlusion sets (green symbols). (f) Same as (c) but for RMS contrast cRMS.