PubMed · 14874247
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L GOUGEROT. 1951-09-13. [Daltonism].. https://pubmed.ncbi.nlm.nih.gov/14874247/
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The color perceived to belong to the illumination of objects is often based on cues from the scene within which the objects are perceived, instead of being based on any view of the source itself. We present measurements of illuminant color estimation by human observers for moving, spectrally filtered spotlights. The results show that when only one illuminant is in the field of view, estimates of illuminant color are seriously biased by the chromaticities of the illuminated surfaces. When the surround of the spotlight is illuminated by a dimmer second light, spotlight matching moves toward veridical in most conditions. Simulations show that a gray-world model cannot be rejected as an adequate explanation for illuminant color estimation and provides as good a fit as a model that gives greater weights to the brightest surfaces. When the surrounding illuminant is brighter than the spotlight, the situation is similar to that of a moving filter. Spotlight matches are close to veridical, and the results can be fit by a model based on estimating both illuminants.
We examined the effect of perceived orientation on the perceived color of matte surfaces in rendered three-dimensional scenes illuminated by a blue diffuse light and a yellow punctate light. On each trial, observers first adjusted the color of a matte test patch, placed near the center of the scene, until it appeared achromatic, and then estimated its orientation by adjusting a monocular gradient probe. The orientation of the test patch was varied from trial to trial by the experimental program, effectively varying the chromaticity of the light mixture from the two light sources that would be absorbed and reemitted by a neutral test patch. We found that observers' achromatic settings varied with perceived orientation but that observers only partially discounted orientation in making achromatic settings. We developed an equivalent illuminant model for our task in which we assumed that observers discount orientation using possibly erroneous estimates of the chromaticities of the light sources and/or their spatial distribution. We found that the observers' failures could be explained by two factors: errors in estimating the direction to the punctate light source and errors in estimating the chromaticities of the two light sources. We discuss the pattern of errors in estimating these factors across observers.
How do human observers estimate the location, form, and color of objects? Accurate estimation is challenging because the light arriving at the eyes depends not only on object properties, but also on the spectra and spatial layout of the light sources (Nassau, 1983; Foley et al., 1990). How well the visual system separates illuminant and object properties to achieve a stable representation has traditionally been studied under the rubric of color and lightness constancy. Most previous work used very simple stimuli, typically a few diffusely illuminated surfaces arranged perpendicular to the line of sight. Over the past several years, however, there has been an evident increase of interest in expanding the conceptualization of this area to incorporate effects that emerge only for complex, typically three-dimensional, scenes. The current issue features papers that represent various manifestations of this interest. One line of research investigates how the three-dimensional layout of a scene affects the perception of lightness and color. Although the current work has long-standing antecedents (e.g. Mach, 1886/1959; Hochberg and Beck, 1954; Gilchrist, 1980), methodological advances in i) experimentation with real illuminated objects (e.g. Brainard et. al, 1987; Rutherford and Brainard, 2002; Ripamonti et al., 2004; Robilotto and Zaidi, 2004), ii) the use of sophisticated graphics simulations (e.g. Yang and Maloney, 1999; Fleming, Dror, & Adelson, 2003; Boyaci, Maloney, & Hersh, 2003; Delahunt and Brainard, 2004), iii) the design of hybrid systems that combine real objects with image-based graphics and video projection (Ling and Hurlbert, 2004), and iv) psychophysical procedures (Maloney and Yang, 2003; Obein, Knoblauch, & Vienot, 2004) have opened the door for systematic exploration of a wider range of phenomena. Recent papers include work on how well vision compensates for changes in surface orientation (Boyaci et al., 2003; Ripamonti et al., 2004), how effectively it discounts inter-reflections among nearby surfaces (Bloj, Kersten, & Hurlbert, 1999; Doerschner, Boyaci, & Maloney, 2004; Delahunt and Brainard, 2004), and how the visual system effectively estimates the spectral properties and spatial layout of the illuminant in three-dimensional scenes (Kraft & Brainard, 1999; Yang & Maloney, 1999; Boyaci, Maloney, & Hersh, 2003; Bloj et al., 2004; Boyaci, Doerschner, & Maloney, 2004; Khang and Zaidi, 2004). The second thread that leads to papers in the current issue is a focus on the functional utility of color and lightness perception -- the idea that these percepts inform us about the properties of objects rather than those of light spectra. This focus resulted in a renaissance of research in color constancy over the past two decades, with particular progress being made in the development of computational models that explore how, in principle, object surface properties can be estimated from image data. As with the experimental lines, early work focused on simple scene geometries (for reviews see Hurlbert, 1998; Maloney, 1999) but consideration has recently expanded to three-dimensional configurations (Adelson and Pentland, 1996; Yang and Maloney, 1999; Bell and Freeman, 2001; Dror, Willsky, & Adelson, 2004) Of particular interest has been the elaboration of purely computational formulations into parametric models of human performance (e.g. Brainard Brunt, & Speigle, 1997; Brainard Kraft, & Longere, 2003; Boyaci et al., 2003; Doerschner et al., 2004; Boyaci et al., 2004; Bloj et al., 2004), tests of how well the visual system exploits image information identified in computational studies (Yang and Maloney, 2001; Delahunt and Brainard, 2004; Smithson and Zaidi, 2004), investigations of how well the visual system recovers perceptual correlates of material properties other than diffuse surface reflectance, such as gloss and translucency (Lu, Koenderink, & Kappers, 2000; Fleming et al., 2003; Pont & Koenderink, 2003; Obein et al., 2004), as well as how geometric aspects of surface reflectance interact with the perception of shape (Fleming et al., 2003).