Perceived lightness, but not brightness, of achromatic surfaces depends on perceived depth information

Abstract

Three experiments wereconducted in an attempt to replicate and clarify Gilchrist's ( ,1980 experiments on the effects of depth information on judgments of achromatic surface color. Gilchrist found that coplanarity, and not retinal adjacency, was the dominant factor in determining achromatic color matches. Because such matches can be made on the basis of either brightness or lightness, we obtained judgments of both qualities. Stereopsis was added to enhance the perceived depth effect of Gilchrist's display, which was otherwise simulated closely on a highresolution CRT. The results for lightness followed the same pattern as those of Gilchrist, but were smaller in magnitude. This discrepancy may reflect reduced extraneous lighting effects in our displays. Our results therefore agree with related studies in suggesting that lightness matches are based on relationships among coplanar surfaces. Brightness matches, however, were not influenced by perceived depth.Achromatic surface perception is modifiable by information specifying depth relations between adjacent surfaces (Gilchrist, , 1980Wist, 1974). Here we report a replication of Gilchrist's impressive demonstrations that large shifts in perceived lightness can be obtained by using depth information to indicate which surfaces are coplanar and which are not. argued that "perceived lightness might be determined primarily by ratios within perceived planes rather than by all retinal ratios regardless of perceived depth" (p. 186). We have also found this to be the case for lightness judgments, but not for brightness judgments.Usage of the terms "lightness" and "brightness" has varied over the years. We will use them here as they have been used in other recent work on surface-color perception (Arend & Goldstein, 1987, in press). Lightness will be used to refer to apparent reflectance, perceptions ranging from blacks through grays to whites. This agrees closely with Evans's (1974) usage. Brightness will be used to refer to perceived luminance, the "overall effective intensity of the stimuli or stimulus" (Evans, 1974, p. 192). These are two distinct, simultaneously available dimensions of experience rather than mutually exclusive " modes" of perception.

We infer light in space

“…1, left). Schirillo et al (1990) found that observers' judgments of the brightness of the gray paper did not vary significantly between the near and far conditions. Instead, because it was actually under a constant level of illumination in both conditions (i.e., the lower level of illumination of the near room), its brightness remained constant across conditions.…”

“…To see how the two distinct qualities of lightness and brightness differ, Schirillo and colleagues (Schirillo, Reeves, & Arend, 1990) repeated Gilchrist's experiment simulated with a special-purpose Tektronix CRT and stereoscope to generate three-dimensional space and the same physical variations in intensity as Gilchrist. Although the main interest was in the difference between lightness and brightness, the data also revealed a striking contrast with those of Gilchrist: While the effects on lightness judgments in the simulation were in the same direction as his, the magnitude was only 41 % of his; that is, the lightness range of the gray paper that appeared in either the near or the far room spanned a 2.7:1 ratio, as compared to his 6.6:1 ratio.…”

The maintenance of apparent luminance of an object.

“…For example, lightness perception can depend on the geometric interpretation of a visual scene, such as curvature (Knill & Kersten, 1991;Pessoa, Mingolla, & Arend, 1996), transparency (Adelson, 1993), and depth (Gilchrist, 1977;Schirillo & Arend, 1995;Schirillo, Reeves, & Arend, 1990). Also, simply inducing the observer to interpret a scene differently (whether a luminance boundary is a shadow or an object border) affects lightness accordingly (Gilchrist, Delman, & Jacobsen, 1983).…”

The perception of lightness in 3-D curved objects

“…Several investigations have shown that brightness matches are not illumination invariant (e.g., Arend & Goldstein, 1987;Jacobsen & Gilchrist, 1988;Schirillo, Reeves, & Arend, 1990). Moreover, for increment conditions where the test region is immediately surrounded by a lower reflectance region, brightness matches follow luminance rather closely.…”