Figure 1.

Some ideas about spatial channels, adaptation and blur. Filter sensitivities (dashed curves) might normally be scaled to give equal responses to the average (1/f ) spectrum of natural images (dashed line in left panel for the norm (N)). Left: adapting to a steeper, blurred spectrum (solid line, A) alters the relative sensitivities across all channels (red curves) so that responses would be renormalized for the new adapting level. This might cause all slopes (blur levels) to appear shallower (sharper; arrows). Right: basis for the repulsion effect. Adaptation of the same tuned mechanisms to a narrowband stimulus (N/A) instead locally depresses sensitivity to the adapting stimulus. This would bias the distribution of responses away from the adapting level toward either lower or higher perceived frequency (arrows).