Parallel detection of violations of color constancy

Foster, David H.; Nascimento, Sérgio M. C.; Amano, Kinjiro; Arend, Larry; Linnell, Karina J.; Nieves, Juan Luis; Plet, Sabrina; Foster, Jeffrey S.

doi:10.1073/pnas.141505198

Cited by 46 publications

(44 citation statements)

References 62 publications

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“…It is not totally clear that observers in this experiment actually equate the appearance of a modified illuminant change with the appearance of a natural illuminant change, 6 but what is clear is that observers are highly sensitive to violations of the invariance of spatial cone-excitation ratios, at least when the two images are presented in quick succession (Linnell & Foster 1996). Indeed, there is evidence that spatial cone-excitation ratios might be an elementary feature extracted from the visual scene (Westland & Ripamonti 2000;Foster et al 2001;Hurlbert & Wolf 2004).…”

Section: (Iv) Coding Colour Relations By Ratiosmentioning

confidence: 83%

Sensory, computational and cognitive components of human colour constancy

Smithson

2005

Phil. Trans. R. Soc. B

184

139

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When the illumination on a scene changes, so do the visual signals elicited by that scene. In spite of these changes, the objects within a scene tend to remain constant in their apparent colour. We start this review by discussing the psychophysical procedures that have been used to quantify colour constancy. The transformation imposed on the visual signals by a change in illumination dictates what the visual system must 'undo' to achieve constancy. The problem is mathematically underdetermined, and can be solved only by exploiting regularities of the visual world. The last decade has seen a substantial increase in our knowledge of such regularities as technical advances have made it possible to make empirical measurements of large numbers of environmental scenes and illuminants. This review provides a taxonomy of models of human colour constancy based first on the assumptions they make about how the inverse transformation might be simplified, and second, on how the parameters of the inverse transformation might be set by elements of a complex scene. Candidate algorithms for human colour constancy are represented graphically and pictorially, and the availability and utility of an accurate estimate of the illuminant is discussed. Throughout this review, we consider both the information that is, in principle, available and empirical assessments of what information the visual system actually uses. In the final section we discuss where in our visual systems these computations might be implemented.

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Section: (Iv) Coding Colour Relations By Ratiosmentioning

confidence: 83%

Sensory, computational and cognitive components of human colour constancy

Smithson

2005

Phil. Trans. R. Soc. B

184

139

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“…It is vitally important from the ecological point of view to distinguish between these (e.g., Gibson, 1979). Human observers have been found to be rather good at distinguishing between changes produced by illumination and reflectance in visual scenes (e.g., Craven & Foster, 1992;Foster et al, 2001;Foster, 2003;Kingdom, 2008).…”

mentioning

confidence: 99%

Lightness constancy and illumination discounting

Logvinenko

Tokunaga

2011

Atten Percept Psychophys

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Contrary to the implication of the term "lightness constancy", asymmetric lightness matching has never been found to be perfect unless the scene is highly articulated (i.e., contains a number of different reflectances). Also, lightness constancy has been found to vary for different observers, and an effect of instruction (lightness vs. brightness) has been reported. The elusiveness of lightness constancy presents a great challenge to visual science; we revisit these issues in the following experiment, which involved 44 observers in total. The stimuli consisted of a large sheet of black paper with a rectangular spotlight projected onto the lower half and 40 squares of various shades of grey printed on the upper half. The luminance ratio at the edge of the spotlight was 25, while that of the squares varied from 2 to 16. Three different instructions were given to observers: They were asked to find a square in the upper half that (i) looked as if it was made of the same paper as that on which the spotlight fell (lightness match), (ii) had the same luminance contrast as the spotlight edge (contrast match), or (iii) had the same brightness as the spotlight (brightness match). Observers made 10 matches of each of the three types. Great interindividual variability was found for all three types of matches. In particular, the individual Brunswik ratios were found to vary over a broad range (from .47 to .85). That is, lightness matches were found to be far from veridical. Contrast matches were also found to be inaccurate, being on average, underestimated by a factor of 3.4. Articulation was found to essentially affect not only lightness, but contrast and brightness matches as well. No difference was found between the lightness and luminance contrast matches. While the brightness matches significantly differed from the other matches, the difference was small. Furthermore, the brightness matches were found to be subject to the same interindividual variability and the same effect of articulation. This leads to the conclusion that inexperienced observers are unable to estimate both the brightness and the luminance contrast of the light reflected from real objects lit by real lights. None of our observers perceived illumination edges purely as illumination edges: A partial Gelb effect ("partial illumination discounting") always took place. The lightness inconstancy in our experiment resulted from this partial illumination discounting. We propose an account of our results based on the two-dimensionality of achromatic colour. We argue that large interindividual variations and the effect of articulation are caused by the large ambiguity of luminance ratios in the stimulus displays used in laboratory conditions.

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“…1a, the illuminants on the left and right are different). In an operational version of this matching task, described in the next section, performance was essentially the same [27].…”

Section: Relative Versus Absolute Judgmentsmentioning

confidence: 99%

“…Performance in one such task has been found to be fast, accurate and effortless, suggesting that some aspects of surface-colour information are processed in parallel over the visual field [27].…”

Section: Relational Colour Constancymentioning

confidence: 99%

“…Such ratios, which can also be calculated across post-receptoral combinations and spatial averages of cone signals, have the remarkable property of being almost exactly invariant under changes in illuminant, both with natural scenes [30] and with artificial scenes of coloured papers [28], and might explain performance in several colour-vision tasks [27,31,32], including asymmetric colour matching [21]. Significantly, they provide a compelling cue to subjects trying to Fig.…”

Section: Relational Colour Constancymentioning

confidence: 99%

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