Shades of 3D Vision
Optics & Photonics Focus
Volume 11 Story 7 - 15/12/2010

Are these images convex or concave?

Examples of the pictures used by Mamassian and coworkers in the experiment where subjects were asked to interpret a 2D image as a 3D object. Surprisingly, our preferred lighting direction is not directly above our heads, but rather slightly shifted to the left [1, 2]. A first hint of this left preference came from art: for over two millennia painters have tended to light their scenes with a left lighting direction, with examples from Roman mosaics, to Renaissance, Baroque and Impressionism [1]. Some experiments by Mamassian and Goutcher have reinforced this idea [2]. According to Mamassian, “although surprisingly robust across observers, the origin of this left bias is still largely a mystery. It is difficult to explain it from an ecological point of view,” like the explanation that light is coming from above because the sun is above our heads, “and as such it challenges the view that we have evolved optimally for our environment.”
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Are these images convex or concave? Examples of the pictures used by Mamassian and coworkers in the experiment where subjects were asked to interpret a 2D image as a 3D object. Surprisingly, our preferred lighting direction is not directly above our heads, but rather slightly shifted to the left [1, 2]. A first hint of this left preference came from art: for over two millennia painters have tended to light their scenes with a left lighting direction, with examples from Roman mosaics, to Renaissance, Baroque and Impressionism [1]. Some experiments by Mamassian and Goutcher have reinforced this idea [2]. According to Mamassian, “although surprisingly robust across observers, the origin of this left bias is still largely a mystery. It is difficult to explain it from an ecological point of view,” like the explanation that light is coming from above because the sun is above our heads, “and as such it challenges the view that we have evolved optimally for our environment.”