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Alexander D Logvinenko

Publications and source records attributed to Alexander D Logvinenko.

13 recordsLinked to original sources
PubMed2006

An effect of luminance contrast on high-spatial-frequency tritanopia.

Luminance contrast was found to affect high-spatial-frequency tritanopia despite the S-cone coordinates of the stimuli being kept constant. This proves that a traditional account of artificial tritanopias based on the spatial resolution differences between the S-cone channel and the M- and L-cone channels is not applicable here. We suggest that the lack of spatial resolution in one of the post-receptor (rather than receptor) spatio-chromatic channels could be a cause of high-spatial-frequency tritanopia.

Color Vision Defects↗
PubMed2006

The proximity structure of achromatic surface colors and the impossibility of asymmetric lightness matching.

In asymmetric lightness matching tasks, observers sometimes report that they cannot achieve satisfactory matches between achromatic surfaces under different neutral illuminants. The surfaces appear different, yet no further adjustment of either surface improves the match. There are evident difficulties in interpreting data from a task that the observer cannot always do, and these difficulties likely affect the interpretation of a large number of previous studies. We investigated, as an alternative to asymmetric matching, the direct use of proximity judgments in the study of surface lightness perception. We asked observers to rate the perceived dissimilarity of pairs of achromatic surfaces that were placed in identical scenes and viewed under different neutral illuminants. We develop a parametric model that accurately predicts perceived dissimilarity in terms of physical light intensities and surface albedos. The parameters of this model are readily interpretable. In particular, the ratio of the influence of changes in illuminant intensity and changes in surface albedo is a measure of the extent to which the observer discounts the illuminant. Asymmetric lightness matching can be interpreted as an unachievable limiting case of proximity judgment.

Color Perception↗
PubMed2005

One blue colour channel or two?

Contrary to the general belief that the yellow-blue mechanism has lower spatial resolution than the red-green mechanism, it has been recently claimed that both mechanisms have similar spatial sensitivity (McKeefry et al, 2001 Vision Research 41 245-255). Studying high-spatial-frequency tritanopia (a colour illusion based on spatio-chromatic interactions in human vision), we found strong evidence for the existence of two blue mechanisms-with low and high spatial-frequency resolution. If confirmed, this may resolve the apparent paradox concerning spatial resolution of the yellow-blue mechanism.

Color Perception↗
PubMed2005

Adelson's tile and snake illusions: a Helmholtzian type of simultaneous lightness contrast.

Adelson's tile, snake, and some other lightness illusions of the same type were measured with the Munsell neutral scale for twenty observers. It was shown that theories based on low-level luminance contrast processing could hardly explain these illusions. Neither can those based on luminance X-junctions. On the other hand, Helmholtz's idea, that simultaneous lightness contrast originates from an error in judgement of apparent illumination, has been elaborated so as to account for the tile and snake illusions as well as other demonstrations presented in this report.

Adult↗
PubMed2005

Does luminance contrast determine lightness?

When presented against a highly lit black background, dimly illuminated white paper strips appear white even when they are equiluminant with the background. Such an example of simultaneous lightness constancy cannot be accounted for by receptor gain control because of the equiluminance. Moreover, this demonstration shows that lightness cannot be reduced to 'relative brightness' as is widely believed.

Computer Simulation↗
PubMed2005

Straightness as a cue for luminance edge interpretation.

In order to determine the reflectance of a surface, it is necessary to discount luminance changes produced by illumination variation, a process that requires the visual system to respond differently to luminance changes that are due to illumination and reflectance. It is known that various cues can be used in this process. By measuring the strength of lightness illusions, we find evidence that straightness is, used as a cue: When a boundary is straight rather than curved, it has a greater tendency to be discounted, as if it were an illumination edge. The strongest illusions occur when a boundary has high contrast and has multiple X-junctions that preserve a consistent contrast ratio.

Attention↗
PubMed2004

Hering's and Helmholtz's types of simultaneous lightness contrast.

Detaching of the test objects from the inducing background was found to reduce significantly Adelson's "snake" lightness illusion but not grating induction. Moreover, the same grating induction effect was measured from 3D real cylinders and a 2D sinewave grating. We conclude that grating induction and Adelson's snake lightness illusion are different types of simultaneous lightness contrast.

Adolescent↗
PubMed2003

Luminance gradient can break background-independent lightness constancy.

A display with a luminance gradient was shown to induce a strong lightness illusion (Logvinenko, 1999 Perception 28 803-816). However, a 3-D cardboard model of this display was found to produce a much weaker illusion (less than half that in the pictorial version) despite the fact that its retinal image is practically the same. This is in line with the hypothesis that simultaneous lightness contrast is solely a phenomenon of pictorial perception (Logvinenko et al, 2002 Perception 31 73-82). The residual lightness illusion in the 3-D model can be accounted for by the fact that this model is a hybrid display. Specifically, while it is a real object, a pictorial representation (of the illumination gradient) is superimposed on it. Thus, lightness in the 3-D display is a compromise between two opposite tendencies: the background-independent lightness constancy and the lightness illusory shift induced by the luminance gradient.

Adolescent↗
PubMed2002

The anchoring effect in lightness perception in humans.

Simultaneous lightness contrast is a classical visual illusion, which has been the focus of research for several generations of visual scientists. Still, there is no agreement on its mechanisms. There are two main competing accounts. The first is descended from ideas of Ewald Hering [Hering, E., Outline of a Theory of the Light Sense, (1874), translated from the German by L. Hurvich and D. Jameson, Harvard University, Cambridge, MA (1964)]. It is based on low-level retinal mechanisms processing the local luminance contrast between the target and the background. The second, originally proposed by Herman von Helmholtz [von Helmholtz, H., Handbuch der Physiologischen Optik, Leipzig, Voss, (1867).] suggests that the illusion is the result of a misjudgement of the illumination. We present a new demonstration, which challenges both explanations. It suggests that simultaneous lightness contrast is not specifically a lightness illusion, being a particular case of a more general phenomenon known as the 'anchoring effect'.

Contrast Sensitivity↗
PubMed2002

Articulation in the context of edge classification.

Many researchers believe the human visual system classifies luminance edges into those produced by reflectance edges or those produced by illumination edges, yet this classification process is not completely understood. One suggestion is that heuristics are used for edge classification. For example. specific contrast relationships at the luminance edge ('codirectional contrast invariance' and 'transversal luminance-ratio preserving') may distinguish an illumination edge from a reflectance edge on the one hand, and from a translucent edge on the other. Distinct from luminance junctions, these features are global characteristics of the luminance pattern that make distinguishing between different types of edge easier with more highly articulated scenes. I demonstrate that apparent translucency, nonreversing X-junctions, and single-reversing X-junctions are insufficient on their own to produce the lightness illusion of Adelson's well-known tile pattern. While tolerating violations of the codirectional contrast invariance and transversal-luminance-ratio presersving without reversing the sign of contrast, the visual system is quite sensitive to such contrast reversal at the luminance edge. I account for this by suggesting that humans process lightness in terms of an ordinal, rather than interval, (or ratio) scale.

Color Perception↗
PubMed2002

Is lightness induction a pictorial illusion?

Lightness induction, or simultaneous lightness contrast (we prefer the term lightness induction since contrast has another meaning in the visual literature, namely, the relative intensity of the stimulation), was studied for a 3-D object (Adelson's wall of blocks) and its 2-D pictorial representations. A statistically significant lightness induction effect was found only for the pictures but not for the 3-D object. No lightness induction effect was found for the 3-D object under either monocular or binocular viewing conditions.

Adolescent↗