Chromatic properties of the colour-shading effect

Kingdom, Frederick A. A.; Rangwala, Sohil; Hammamji, Karim

doi:10.1016/j.visres.2004.11.023

Cited by 23 publications

(40 citation statements)

References 27 publications

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“…However, this choice of HM grating was arbitrary. Kingdom et al (2005) showed that the colour direction of both the depth-enhancing and depth-suppressing chromatic gratings in the colour-shading effect was unimportant: it was their colour contrast that mattered. For this reason the details of the generation of the HM grating will not be given here, but the interested reader can consult the aforementioned article.…”

Section: Stimulimentioning

confidence: 99%

“…The 'colour-shading effect' (Kingdom, 2003;Kingdom et al, 2005) is a recent example of this approach. When a chromatic grating is added to a differentlyoriented luminance grating, one obtains an impression of a corrugated surface -an instance of 'shape-from-shading'.…”

Section: Introductionmentioning

confidence: 99%

“…In our two previous studies of the colour-shading effect (Kingdom, 2003;Kingdom et al, 2005), subjects adjusted the amplitude of a random-element, disparitymodulated stereo-grating to match the perceived depth of the corrugations in the plaid patterns. One criticism of this method is that binocular viewing the patterns may have obscured subtle depth differences because stereo-vision would signal 'flat'.…”

Section: Introductionmentioning

confidence: 99%

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Colour contrast influences perceived shape in combined shading and texture patterns

Kingdom¹,

Wong²,

Yoonessi³

et al. 2006

Spatial Vis

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The 'colour-shading effect' describes the phenomenon whereby a chromatic pattern influences perceived shape-from-shading in a luminance pattern. Specifically, the depth corrugations perceived in sinusoidal luminance gratings can be enhanced by spatially non-aligned, and suppressed by spatially aligned sinusoidal chromatic gratings. Here we examine whether colour contrast can influence perceived shape in patterns that combine shape-from-shading with shape-from-texture. Stimuli consisted of sinusoidal modulations of texture (defined by orientation), luminance and colour. When the texture and luminance modulations were suitably combined, one obtained a vivid impression of a corrugated depth surface. The addition of a colour grating to the texture-luminance combination was found to enhance the impression of depth when out-of-phase with the luminance modulation, and suppress the impression of depth when in-phase with the luminance modulation. The degree of depth enhancement and depth suppression was approximately constant across texture amplitude when measured linearly. In the absence of the luminance grating however, the colour grating had no phase-dependent affect on perceived depth. These results show that colour contrast modulates the contribution of shading to perceived shape in combined shading and texture patterns.

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Section: Stimulimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Colour contrast influences perceived shape in combined shading and texture patterns

Kingdom¹,

Wong²,

Yoonessi³

et al. 2006

Spatial Vis

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“…Therefore, our brains do not rely on the physics of the real world to interpret shadows [29]. Furthermore, our brains do not even require the wavelength composition of shadows to be consistent with plausible illumination conditions: We simply require local regions to be relatively darker, and of relatively desaturated color [30]; in fact, the shadow itself can be of any color as long as these rules are met, as the Fauvists showed, and Kingdom et al recently confirmed [31].One reason why shadows, perspective, and reflection may not need to be physically accurate for an acceptable impression of depth, transparency, or shine is that the visual system evolved under conditions in which these features are not stable and not consistent within a scene over time: Shadows change as daylight changes (hence the inconsistencies of shadows in impressionist paintings, which were often painted outdoors over a stretch of time during which the sun and shadows move); similarly, perspective and reflections change second to second as we move our eyes across a scene. Therefore, there would have been little biological benefit to incorporate the rules for global perspective or illumination into our visual computations.…”

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confidence: 97%

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confidence: 98%

Perspectives on science and art

Conway¹,

Livingstone²

2007

Current Opinion in Neurobiology

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Artists try to understand how we see, sometimes explicitly exploring rules of perspective or color, visual illusions, or iconography, and conversely, scientists who study vision sometimes address the perceptual questions and discoveries raised by the works of art, as we do here.The integration of visual art with the experimental study of vision has its roots in formal analysis of painting, but this approach has gone out of vogue in art-historical circles because it ignores the impact of cultural context on art appreciation. Advances in our understanding of how the brain works have resuscitated interest in linking art with vision science. Here we review some of these new links, with the caveat that we will not address visual aesthetics, but rather some nuts and bolts of making and looking at art, in an endeavor to enrich our understanding of art 'in much the same way as a knowledge of bones and muscles has for centuries enhanced the ability of artists to portray the human body' [1]. Some recent studies may even illuminate why cultural context is so important in visual art.When we look at the world, or at a work of art, our eyes, and our visual attention, are constantly and alternately moving and fixating [2]. Our fixations are not randomly distributed across a scene, but rather concentrate on key regions-to a first approximation, on the areas of high local contrast [3]. The visual machinery that directs the eyes where to look can have two impacts on art. On the one hand, artists have developed techniques to direct your gaze; on the other hand, the unconscious machinery directing the gaze of the artist may influence which parts of the scene the artist portrays or emphasizes. Leonards et al. [4] have argued that Renaissance artists used gold for its special reflective quality under candlelight to control the viewers' gaze. The authors argue that 'the glow of the gold induced shifts in fixations to symbolically important regions of the painting' (Figure 1). Candle illumination introduces areas of local contrast that is not apparent under daylight conditions-the thin lines of gold extending into the bodies of the two subjects. It is these regions that show increased fixations under low illumination, raising the possibility that the viewer's gaze and attention are drawn to these regions not because of their symbolism, as Leonards et al. argue, but rather because of their low-level visual salience.Eyes are especially potent in attracting the gaze, both because of their behavioral significance and because they are the regions of high local contrast. Tyler [5•] examined 265 portraits spanning the past 600 years and found a strong tendency for one eye to be centered on the vertical midline of the painting (Figure 2). A recent critique of Tyler's observations asserts that 'one eye tends to be relatively close to the vertical midline because of geometric constraints on the placing of a relatively large object, the head, within a pictorial frame' suggesting that there is no behavioral significance to eye-centering [...

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