To compute lightness, illumination is not estimated, it is held constant.

Gilchrist, Alan

doi:10.1037/xhp0000487

Cited by 9 publications

(9 citation statements)

References 39 publications

(73 reference statements)

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“…However, Gilchrist (2018) argued that Boyaci et al's (2003) results can be explained by the relaxed coplanar principle (Gilchrist, 1977), which hypothesizes that lightness is determined by luminance ratios with surrounding surfaces, and this effect is stronger as the surrounding surface becomes more parallel to the target plane. This observation suggests that the estimates of illumination need not be considered explicitly to explain Boyaci et al's results.…”

Section: Discussionmentioning

confidence: 99%

Distinct processes of lighting priors for lightness and 3-D shape perception

Kobayashi¹,

Zavagno²,

Morikawa³

2020

Preprint

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The visual system often relies on prior assumptions when interpreting ambiguous visual inputs. A well-known example is the light-from-above prior, which aids the judgment of an object’s three-dimensional (3-D) shape (i.e., convex or concave). Recent studies have revealed that the light-from-above prior also helps solve lightness ambiguity. This study aimed to examine whether 3-D shape perception and lightness perception share the same lighting prior. The study participants performed two tasks: one focusing on lightness perception and another focusing on 3-D shape perception. The dominant directions of the assumed lighting were calculated from participants’ performance in the two tasks. The results showed that the assumed lighting direction for 3-D shape perception considerably shifted toward the left while the one for lightness perception was almost from directly above. The clear difference between these two directions supports the hypothesis that the visual system uses distinct lighting priors for 3-D shape perception and lightness perception. Japanese and European observers then replicated these results, indicating that the lighting priors are universal regardless of reading/writing direction.

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Section: Discussionmentioning

confidence: 99%

Distinct processes of lighting priors for lightness and 3-D shape perception

Kobayashi¹,

Zavagno²,

Morikawa³

2020

Preprint

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“…Although this study may appear to support the idea that an internal representation of illumination is relevant to lightness perception (i.e., the albedo hypothesis), a long discussion on whether illumination affects lightness perception must be noted (Agostini & Galmonte, 2002; Gilchrist, 2006; Schirillo, 2013; Zavagno & Daneyko, 2012; Zavagno, Daneyko, & Sakurai, 2011). Studies have argued that complex processing that collects illumination cues and subsequently constructs representations does not play a role in lightness processing (e.g., Gilchrist, 2006, 2018). This study is in favor of the albedo hypothesis, but the prior assumption about illumination from a single direction does not need immediate visual information and does seem to be simpler and more effortless than processing for the albedo.…”

Section: Discussionmentioning

confidence: 99%

“…For example, considering the complexity of actual environmental illumination and that the modern world is filled with multiple artificial lights and light-occluding objects, estimation of illumination from the environment may require considerably high-level knowledge and is unlikely to influence lightness perception (Gilchrist, 2006). Moreover, the data that apparently support the illumination estimate theory can be explained by the existing low- or mid-level-based theories (Gilchrist, 2018). Some studies have argued that lightness perception can be affected by accrued knowledge (Levin & Banaji, 2006), but Firestone and Scholl (2015, 2016) have disagreed.…”

Section: Introductionmentioning

confidence: 90%

An Upward-Facing Surface Appears Darker: The Role Played by the Light-From-Above Assumption in Lightness Perception

Kobayashi

Morikawa

2019

Perception

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The human visual system can extract information on surface reflectance (lightness) from light intensity; this, however, confounds information on reflectance and illumination. We hypothesized that the visual system, to solve this lightness problem, utilizes the internally held prior assumption that illumination falls from above. Experiment 1 showed that an upward-facing surface is perceived to be darker than a downward-facing surface, proving our hypothesis. Experiment 2 showed the same results in the absence of explicit illumination cues. The effect of the light-from-left prior assumption was not observed in Experiment 3. The upward- and downward-facing surface stimuli in Experiments 1 and 2 showed no difference in a two-dimensional configuration or three-dimensional structure, and the participants’ perceived lightness appeared to be affected by the observers’ prior assumption that illumination is always from above. Other studies have not accounted for this illusory effect, and this study’s finding provides additional insights into the study of lightness perception.

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“…Spatial localization of assumptions about the illumination makes sense in complex scenes in which the illumination cannot be considered to be uniform, such as in many natural scenes (Gilchrist & Radonjic, 2010;Nascimento, Amano, & Foster, 2016). In our simple configuration it is perhaps somewhat surprising, but the idea that the illumination is only assumed to be uniform within small regions, even in quite simple scenes, is not new (Gilchrist, 2018;Land & McCann, 1971;Radonjić & Gilchrist, 2013).…”

Section: Conclusion and Discussionmentioning

confidence: 93%

Neighboring chromaticity influences how white a surface looks

2019

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To identify surface properties independently of the illumination the visual system must make assumptions about the statistics of scenes and their illumination. Are assumptions about the intensity of the illumination independent of assumptions about its chromaticity? To find out, we asked participants to judge whether test patches within three different sets of surrounding surfaces were white or grey. Two sets were matched in terms of their maximal luminance, their mean luminance and chromaticity, and the variability in their luminance and chromaticity, but differed in how luminance and chromaticity were associated: the highest luminance was either associated with colorful surfaces or with achromatic ones. We found that test patches had to have a higher luminance to appear white when the highest luminance in the surrounding was associated with colorful surfaces. This makes sense if one considers that being colorful implies that a surface only reflects part of the light that falls on it, meaning that the illumination must have a higher luminance (a perfectly white surface reflects all of the light falling on it). In the third set, the colorful surfaces had the same luminance as in the set in which they were associated with the highest luminance, but the achromatic surfaces had a lower luminance so that the overall mean luminance was lower. Despite the constraints on the illumination being identical, test patches did not have to have as high luminance to appear white for the third set. Considering the layout of the surfaces in the surrounding revealed that test patches did have to have the same high luminance if the high luminance colorful surfaces were adjacent to the target patch. Thus, the assumptions about the possible illumination are applied locally. A possible mechanism is relying on the contrast within each type of cone: for a surface to appear white it must stimulate each of the three kinds of cones substantially more than do any neighboring surfaces.

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To compute lightness, illumination is not estimated, it is held constant.

Cited by 9 publications

References 39 publications

Distinct processes of lighting priors for lightness and 3-D shape perception

Distinct processes of lighting priors for lightness and 3-D shape perception

An Upward-Facing Surface Appears Darker: The Role Played by the Light-From-Above Assumption in Lightness Perception

Neighboring chromaticity influences how white a surface looks

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