Fig. 7.

The experimental results of Georgeson et al. (2007) on the matching of two-component blurred edges are shown by red symbols on the right. The horizontal axis shows the ratio of contrasts between the less-blurred to the more-blurred edge, and the vertical axis shows the blur of the Gaussian-blurred edge that was selected by the observer to be the best match. The left-hand top panel shows the second-derivatives of the edges used in the experiments: red, 15 arcmin; green, 5 arcmin; blue, magenta, average blur. In addition, a blue curve shows the edge with equal amplitude mixtures, but it is hard to see as it is coincident with the smallest blur. The bottom panels show profiles and results when the component blurs were doubled to 30 arcmin (red) and 10 arcmin (green). The red curve on the right shows the predictions of a model in which blur is encoded in the separation between peaks and troughs in the second-derivative. It predicts too high a dominance of the less-blurred edge. The green curve shows the same prediction but in the presence of intrinsic blur.