On the determinants of surface brightness

Abstract

In the present study, the luminance determinants of surface brightness were explored. The findings that uniform surfaces vanish when their retinal contour is stabilized and that on-center and off-center visual neurons signal the luminance step at the border of surfaces support the current view that this luminance step determines surface brightness (Arend, Buehler, & Lockhead, 1971;Fiorentini, Baumgartner, Magnussen, Schiller, & Thomas, 1990;Grossberg & Todorović, 1988;Krauskopf, 1963;Land & McCann, 1971;Ross & Pessoa, 2000). However, here it is shown that a reanalysis of the experimental results reported by Beck (1974) and Kozaki (1973) reveals that absolute luminances determine surface brightness independently of the luminance step at the border of surfaces. EXPERIMENT 1Experiment 1 was designed to replicate the results of Beck (1974) and Kozaki (1973) using a broader range of stimulus parameters.Surfaces presented in a dark field were used. Since, in these surfaces, whiteness matches brightness (Redding & Lester, 1980) and is complementary to blackness (Quinn, Wooten, & Ludman, 1985), the effects of absolute luminances on each of these attributes were tested. 1 MethodParticipants. Forty-eight students of the University of Padua with normal or corrected-to-normal vision participated to fulfill a course requirement.Stimuli. In a dark room, each stimulus appeared on the frontal parallel 33 3 25 cm screen of an Apple monitor controlled by a Macintosh 7200 computer. The viewing distance was about 80 cm.The stimulus was a 4.5 3 4.5 cm achromatic square in the middle of an achromatic background covering the entire screen. Let S and B denote the luminance of the square and that of the background, respectively. There were 30 stimuli, one for each different pair of S and B, in which S was 10, 20, 40, 60, or 80 cd/m 2 and B was 1, 15, 30, 50, 70, or 110 cd/m 2 . The stimuli remained on the screen until the experimenter typed the participant's response. The intertrial interval was 3 sec.Procedure. The experiment was divided into three sessions. During presentation of the instructions for each session, a horizontal row of eight equidistant 2.2 3 2.2 cm achromatic squares with luminances of 0. 05, 5, 10, 20, 40, 70, 100, and 140 cd /m 2 , increasing from left to right, was displayed on a background with B = 15 cd/m 2 . In the first session, the participants rated the perceived amount of light coming from the square of each stimulus using integers from 0 to 100, with 0 representing the brightness of the leftmost square and 100 that of the rightmost square in the row of eight squares. In the remaining two sessions, the participants rated the perceived amount either of whiteness or of blackness in the square of each stimulus using integers from 0 to 100, with 0 representing the absence of white or of black and 100 representing the presence only of white or only of black. Half of the participants rated whiteness in the second session and blackness in the third. For the other half, the order was reversed. In each session, the se...

Do Cortical Neurons Process Luminance or Contrast to Encode Surface Properties?

“…Indeed, theoretical studies support roles for both local luminance (Gilchrist 1999;Pessoa et al 1995) and mean luminance (Land and McCann 1971;Robilotto and Zaidi 2004) in determining aspects of brightness and lightness perception. More generally, if no luminance information were to reach visual cortex, animals would be unable to estimate overall light level (Barlow and Verrillo 1976;Masin 2003). Previous reports of cortical neurons that respond to Ganzfield luminance stimuli (Kayama et al 1979;Maguire and Baizer 1982) are also consistent with the notion that both luminance and contrast play important roles in determining surface brightness.…”

“…Related computational approaches advocate the filling-in of contrast information within the regions defined by object boundaries (Cohen and Grossberg 1984;Gerrits and Vendrik 1970;Grossberg and Todorovic 1988), a process that is generally assumed to occur in the visual cortex (Grossberg and Mingolla 1985;Komatsu et al 2000Komatsu et al , 2002Pessoa et al 1998). Recent psychophysical studies, however, have shown that the tendency toward brightness constancy can be relatively weak (Masin 2003), even in complex displays (Arend and Spehar 1993a,b;Robilotto and Zaidi 2004). Furthermore, classical experiments with Ganzfeld stimuli indicate that human observers can act like photometers in the absence of contrast information (Barlow and Verrillo 1976).…”

Information integration study of Metelli's and Morinaga's theories of achromatic transparency

“…implicitly assume that information about A , P , Q , and B is preserved in the visual cortex in agreement with current psychophysical and neurophysiologic evidence (Knau, 2000; Masin, 2003; Roe, Lu, & Hung, 2005; Vladusich, Lucassen, & Cornelissen, 2006). The present study tested the validity of .…”

“…The letters represent the luminance of the respective area in Figure 1. (Knau, 2000;Masin, 2003;Roe, Lu, & Hung, 2005;Vladusich, Lucassen, & Cornelissen, 2006). The present study tested the validity of Equations 3 and 4.…”

The place of white in a world of grays: A double-anchoring theory of lightness perception.

“…In keeping with the weight/luminance rule, we shall then expect a smaller weighting at the surround step. (For independent evidence for the importance of absolute luminance in lightess computation, see Masin, 2003b.) The second is that the luminance range of the squares and the luminance range in the laboratory become the same.…”