The fragile edges of block averaged portraits

The blocky faces painted by Chuck Close and the block-averaged portraits produced by Harmon and Julesz provide a strong counter to the assumption of scale independence in visual perception. When either Chuck Close’s or Harmon and Julesz’z portraits are viewed from a great distance, it is indistinguishable from a unmnanipulated photograph of the subject. As one approaches the portrait it still appears to be a complete three-dimensional face despite the fact that the grid made by the blocks is still visible. Scale independence predicts that when the same portrait is viewed up close, one would continue to see a three dimensional face. However when the portrait is viewed at short viewing distances, the face looses its tree dimensional quality and collapses into a grid of flat marks. We hypothesize that the transition between percept of the grid and the percept of the face is determined by the relative amount of energy in the grid and in the face. According to this hypothesis, increasing the energy in the grid, independently from the energy of the face, will bias the observer towards seeing blocks. Furthermore changing the contrast of the image will decrease the energy of both the grid and of the face to the same degree, we hypothesize that there would be no change in the observer’s bias towards seeing the blocks or the face. The result of all of the manipulations is a decrease in how readily the face collapses compared to the unmanipulated condition. The collapse of the face is not determined by the relative amount of energy in the block and in the face, instead there is something special about the conditions created by unmanipulated block averaging results in the strongest bias towards seeing the blocks