Edge-Based Shading as a Depth Cue in Paintings

We explored how an artist who uses a particular monochrome modern painting style generates the impression of relief in paintings. Three portraits, painted after model, were created especially for the experiment. Photographs of the paintings were presented on a computer screen. To investigate the perceived relief of observers we used a gauge figure task. We expected an effect of background contrast on perceived total depth range of the relief, because this is well known in the case of photography. We found that the contrast with the color of the canvas, white, gray or black, influences the perceived articulation of the relief but does not influence the perceived total depth range of the relief. The major difference between photographs and these paintings is that contrasts in the paintings are built up through edge-based shading, whereas photographs mostly contain tonal-area shading. The classical shape from shading cue does not apply to the impressions of depth evoked by the paintings. Perhaps surprisingly edge-based shading can be as effective as classical ways of creating pictorial relief.