Measuring the meter: on the constancy of lightness scales seen against different backgrounds

Abstract

The constancy of a 16-step achromatic Munsell scale was tested with regards to background variations in two experiments. In experiment 1 three groups of observers were asked to find lightness matches for targets in simultaneous lightness displays by using a 16-step achromatic Munsell scale placed on a white, black, or white-black checkered background. In experiment 2, a yellow-blue checkered background and a green-red checkered background replaced Munsell scales on the black and on the white backgrounds. Significant effects of scale background on matches were found only in experiment 1, suggesting that background luminance is a crucial factor in the overall appearance of the scale. The lack of significant differences in experiment 2, however, may stand for an overall robustness of the scale with respect to background luminance changes occurring within certain luminance ranges.

The Influence of Physical Illumination on Lightness Perception in Simultaneous Contrast Displays

“…A matching method was used with a 16-step lightness scale ranging from Munsell n.v. 2.0 to 9.5 ( Zavagno, Daneyko, & Agostini, 2011 ). Such a scale was seen against a printed black–white checkerboard background and inserted inside a viewing box ( Figure 3 ) with its own constant illumination that had no effect on the laboratory’s illumination.…”

“…For a review on this topic, see Kingdom (2011) . Here, we do not focus on the different theoretical stances about the relationship between lightness and perceived illumination; rather, we address the effect that the intensity of physical illumination has on lightness perception, separately from other factors in the perception of illumination ( Zavagno, Daneyko, & Sakurai, 2011 ).…”

“…Nevertheless, they were actually speaking about achromatic surface color; hence, the appropriate term nowadays is ‘lightness constancy’. In fact, given the conceptualization of brightness in terms of perceived luminous energy, the term brightness constancy is a chimera from a theoretical point of view, as brightness is most often tightly correlated with luminance ( Zavagno et al., 2011 ). 1 Jameson and Hurvich reported in their study a slight increase in lightness matchings as the illumination over the targets was increased, except for two of their targets, a middle and a dark gray target.…”

“…For instance, Gilchrist et al. (1999) developed a theory that can account for simultaneous contrast without the need to refer to illumination as a mediated top-down construct; Rudd (2010; Experiment 2) showed that observers can estimate brightness by filtering out contrast induction, thus showing that observers can distinguish between lightness and brightness even in contrast displays; Zavagno et al. (2011) offered logical arguments against the notion of “brightness constancy” and its usefulness in perceptual terms.…”

Mishaps, errors, and cognitive experiences: on the conceptualization of perceptual illusions

“…The Gestalt and the Ecological approaches share a common indifference towards the notion of veridicality, but for different reasons: if for the Ecological approach such concept is unnecessary , for the Gestalt approach it is irrelevant , given that there is no way to establish whether a percept is veridical with respect to the distal source of stimulation, as knowledge of such source comes from the percept itself, or is mediated by the use of some instrumentation, which however cannot tell what is more veridical. Moreover physical properties of a distal stimulus are only rough correlates of what is perceived (Zavagno et al, 2011a , b ). For instance, the luminance of an achromatic surface is the physical correlate of lightness (achromatic surface color), which however, does not correlate with the luminance of the physical surface: a sheet of paper with reflectance 70% may appear light gray even if its luminance changes dramatically, because lightness is a contextual experience, functional to the characteristics of the scene in relation to the perceiver.…”