Constructed in the studio, contemporary photographer Robert Cumming's conceptual images of the 1970s often take shape as pseudo-scientific presentations, witty jokes with deeply layered meanings that address our notions of perception and illusion. This example is a false diptych that purports to be a demonstration of the scientific phenomenon described in its title. In the picture, a real stool, in bright sunlight, is shown next to its image, which seems to vibrate optically beside it. But the "afterimage" (in reality, an evanescent phenomenon) is here a spray-painted illusion, falsified "proof" that contrasts with the truthfulness of the photograph. Cumming willingly revealed his joke by including the aerosol paint can in the picture.

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