Pictorial spacecrafts - the Ames' Glass

There are various ways to evoke stereopsis without binocular disparities. Closing one eye, or looking through a synopter are well-known methods. Ames (1925) listed nine ways of generating this so-called ''plastic effect," one of which involves a cylindrically curved lens placed in front of one eye. We investigated qualitative perceptual effects of this particular way of viewing artworks. A total of 38 participants viewed three digitally reproduced paintings. Initially, they were asked to spontaneously report the perceptual effect of the lens. While being naive to the purpose of the experiment, 66% of the participants reported increased depth experience. In addition, participants reported increased contrast, color vibrancy, and material expression (e.g., increased shininess). During a second part of the experiment, we asked to report on seven qualities: depth, color, three-dimensional shape, realism, detail, light, and material. All qualities increased significantly except detail, which seemed to show idiosyncratic results: the majority of the observers experienced a decrease of detail, while a minority reported, surprisingly, an increase of detail. The results agree with previous qualitative accounts on monocular aperture viewing, despite relying on entirely different nonpictorial cues: monocular aperture viewing relies on the absence of vergence and binocular disparities, whereas the Ames' Glass relies on distorted binocular disparities while keeping vergence unchanged. Together with the synopter, for which qualitative data is lacking, the Ames Glass and monocular aperture viewing are pictorial spacecrafts fit for art gallery viewing.