The Square-Wave Illusion and Phase Anisotropy of the Human Visual System

Perception ◽  
1982 ◽  
Vol 11 (5) ◽  
pp. 547-556 ◽  
Author(s):  
Lawrence E Leguire ◽  
Randolph Blake ◽  
Michael Sloane
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Relative Phase ◽  
Adaptation Effect ◽  
Phase Relations ◽  
Phase Anisotropy ◽  
Triangular Wave ◽  
Square Wave ◽  
Frequency Components ◽  
Over Time

A triangular-wave grating is perceived to fluctuate over time: at one moment it may appear veridical (ie triangular), at another it may more closely resemble a square-wave grating with rounded edges. In addition, the square-wave illusion itself is bistable, in that it sometimes appears to shift in phase by 180 deg. Experiments in which the phase and amplitude of the first three frequency components of the triangular-wave grating were independently varied showed that the square-wave illusion results from the relative phase of the frequency components. Adaptation to two frequency components in square-wave (sine) phase was found to reduce the illusion strength, and adaptation to triangular-wave (cosine) phase was found to increase the illusion strength. In addition, the square-wave adaptation effect spreads to nonadapted retinal areas. It is concluded that the square-wave illusion reflects a phase anisotropy in the human visual system that favors square-wave phase over other phase relations.

A Test of the Spatial-Frequency Explanation of the Müller-Lyer Illusion

Perception ◽  
1986 ◽  
Vol 15 (5) ◽  
pp. 553-562 ◽  
Author(s):  
Marisa Carrasco ◽  
Jesus G Figueroa ◽  
J Douglas Willen
Keyword(s):  
Spatial Frequency ◽  
Visual System ◽  
Human Visual System ◽  
Lyer Illusion ◽  
Lower Spatial Frequency ◽  
Spatial Frequencies ◽  
Frequency Components ◽  
Fourier Spectra

Previous investigations have shown that the response of spatial-frequency-specific channels in the human visual system is differentially affected by adaptation to gratings of distinct spatial frequencies and/or orientations. A study is reported of the effects of adaptation to vertical or horizontal gratings of a high or a low spatial frequency on the extent of the Brentano form of the Müller-Lyer illusion in human observers. It is shown that the illusion decreases after adaptation to vertical gratings of low spatial frequency, but seems unaffected otherwise. These results are consistent with the notion of visual channels that are spatial-frequency and orientation specific, and support the argument that the Müller-Lyer illusion may be due primarily to lower-spatial-frequency components in the Fourier spectra of the image.

The Aperture Capture Illusion

2017 ◽  
Author(s):  
Evan M. Palmer ◽  
Philip J. Kellman
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Related Factors ◽  
Perceptual Illusion ◽  
Object Shape ◽  
Occluded Objects ◽  
Over Time

Perception of object shape is typically accurate and robust, even when objects move behind occluding surfaces, thus fragmenting their visible regions across space and over time. However, when an object is seen moving behind an occluding surface with only two misaligned apertures, a striking perceptual illusion occurs. The object appears distorted in the same direction as the offset of the apertures. This “aperture capture illusion” reveals the limits of spatiotemporal object formation and gives clues as to how the human visual system perceives dynamically occluded objects under normal circumstances. These concepts as well as related factors are explored in this chapter.

The Effects of Temporal Modulation on the Orientation Channels of the Human Visual System

Perception ◽  
1973 ◽  
Vol 2 (1) ◽  
pp. 23-29 ◽  
Author(s):  
C R Sharpe ◽  
D J Tolhurst
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Adaptation Effect ◽  
Half Width ◽  
Temporal Modulation ◽  
Spatial Adaptation ◽  
Temporal Properties ◽  
Spatial Frequencies ◽  
Sinusoidal Gratings ◽  
Orientation Specificity

The orientation specificity of spatial adaptation was quantified by using an equivalent-contrast transformation. The half-width at half-amplitude of the adaptation effect was 6·5° when the sinusoidal gratings were stationary, but was increased to 11° when the gratings drifted laterally. Another type of temporal modulation, flashing the gratings on and off repetitively, also increased the half-width, but only at low spatial frequencies where these stimuli actually appeared to be flickering back and forth at threshold. At higher spatial frequencies the flashing stimuli appeared to be stationary at threshold and the half-width was as small as that for truly stationary gratings. It is suggested that there are two types of channel in the visual system: they differ in their orientation specificities, in their temporal properties, and in their roles in the analysis of a spatiotemporal stimulus.

Evaluation of the Human Visual System in Cosmetics Foundation Colour Selection

2020 ◽  
Vol 2020 (1) ◽  
pp. 60-64
Author(s):  
Altynay Kadyrova ◽  
Majid Ansari-Asl ◽  
Eva Maria Valero Benito
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Skin Tone ◽  
Skin Colour ◽  
Psychophysical Experiment ◽  
Spectral Measurements ◽  
Practical Applications ◽  
Subjective Evaluations ◽  
Colour Measurements ◽  
Colour Quantification

Colour is one of the most important appearance attributes in a variety of fields including both science and industry. The focus of this work is on cosmetics field and specifically on the performance of the human visual system on the selection of foundation makeup colour that best matches with the human skin colour. In many cases, colour evaluations tend to be subjective and vary from person to person thereby producing challenging problems to quantify colour for objective evaluations and measurements. Although many researches have been done on colour quantification in last few decades, to the best of our knowledge, this is the first study to evaluate objectively a consumer's visual system in skin colour matching through a psychophysical experiment under different illuminations exploiting spectral measurements. In this paper, the experiment setup is discussed and the results from the experiment are presented. The correlation between observers' skin colour evaluations by using PANTONE Skin Tone Guide samples and spectroradiometer is assessed. Moreover, inter and intra observer variability are considered and commented. The results reveal differences between nine ethnic groups, between two genders, and between the measurements under two illuminants (i.e.D65 and F (fluorescent)). The results further show that skin colour assessment was done better under D65 than under F illuminant. The human visual system was three times worse than instrument in colour matching in terms of colour difference between skin and PANTONE Skin Tone Guide samples. The observers tend to choose lighter, less reddish, and consequently paler colours as the best match to their skin colour. These results have practical applications. They can be used to design, for example, an application for foundation colour selection based on correlation between colour measurements and human visual system based subjective evaluations.

Objective Video Quality Method Based on Mutual Information and Human Visual System

2012 ◽  
Vol 58 (2) ◽  
pp. 147-152
Author(s):  
Michal Mardiak ◽  
Jaroslav Polec
Keyword(s):  
Mutual Information ◽  
Visual System ◽  
Human Visual System ◽  
Quality Evaluation ◽  
Video Quality ◽  
Evaluation Criteria ◽  
Test Sequence ◽  
Quality Metric ◽  
Two Stages ◽  
Video Quality Metric

Objective Video Quality Method Based on Mutual Information and Human Visual SystemIn this paper we present the objective video quality metric based on mutual information and Human Visual System. The calculation of proposed metric consists of two stages. In the first stage of quality evaluation whole original and test sequence are pre-processed by the Human Visual System. In the second stage we calculate mutual information which has been utilized as the quality evaluation criteria. The mutual information was calculated between the frame from original sequence and the corresponding frame from test sequence. For this testing purpose we choose Foreman video at CIF resolution. To prove reliability of our metric were compared it with some commonly used objective methods for measuring the video quality. The results show that presented objective video quality metric based on mutual information and Human Visual System provides relevant results in comparison with results of other objective methods so it is suitable candidate for measuring the video quality.

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