Identification of Two-Tone Images; Some Implications for High- and Low-Spatial-Frequency Processes in Human Vision

Perception ◽  
1988 ◽  
Vol 17 (4) ◽  
pp. 429-436 ◽  
Author(s):  
Anthony Hayes
Keyword(s):  
Spatial Frequency ◽  
Human Vision ◽  
Positive Form ◽  
Line Drawings ◽  
Geometric Figures ◽  
Spatial Frequencies ◽  
Negative Images ◽  
Frequency Components

Unlike most multitone images, two-tone images such as print, geometric figures, and line drawings are as easy to interpret in photographic negative as in positive form. However, images derived from a multitone original in which intensity values are quantised to two levels are not. Bi-level quantised images, distinct from most other two-tone images, are shown to contain picture related components in their low spatial frequencies. Since it is the low-spatial-frequency components alone of negative images that present difficulties for vision, it is proposed that images which are as easy to interpret in negative as in positive form are those which are readily identified using only their high spatial frequencies.

Recognition of Positive and Negative Bandpass-Filtered Images

Perception ◽  
1986 ◽  
Vol 15 (5) ◽  
pp. 595-602 ◽  
Author(s):  
Tony Hayes ◽  
M Concetta Morrone ◽  
David C Burr
Keyword(s):  
Spatial Frequency ◽  
Visual System ◽  
Visual Information ◽  
Recognition Performance ◽  
Low Frequency ◽  
High Spatial Frequency ◽  
Spatial Frequencies ◽  
Negative Images ◽  
Frequency Components

A study is reported in which the significance for vision of low- and high-spatial-frequency components of photographic positive and negative images was investigated by measuring recognition of bandpass-filtered photographs of faces. The results show that a 1.5 octave bandpass-filtered image contains sufficient visual information for good recognition performance, provided the filter is centred close to 20 cycles facewidth−1. At low spatial frequencies negatives are more difficult to recognize than positives, but at high spatial frequencies there is no difference in recognition, implying that it is the low-frequency components of negatives which present difficulties for the visual system.

Orientation Specificity and Spatial Selectivity in Human Vision

Perception ◽  
1973 ◽  
Vol 2 (1) ◽  
pp. 53-60 ◽  
Author(s):  
J A Movshon ◽  
C Blakemore
Keyword(s):  
Spatial Frequency ◽  
Human Visual System ◽  
Human Vision ◽  
Orientation Tuning ◽  
High Contrast ◽  
Vertical Grating ◽  
Spatial Frequencies ◽  
High Contrast Grating ◽  
Orientation Specificity ◽  
Adaptation Method

An adaptation method is used to determine the orientation specificity of channels sensitive to different spatial frequencies in the human visual system. Comparison between different frequencies is made possible by a data transformation in which orientational effects are expressed in terms of equivalent contrast (the contrast of a vertical grating producing the same adaptational effect as a high-contrast grating of a given orientation). It is shown that, despite great variances in the range of orientations affected by adaptation at different spatial frequencies (±10° to ±50°), the half-width at half-amplitude of the orientation channels does not vary systematically as a function of spatial frequency over the range tested (2·5 to 20 cycles deg−1). Two subjects were used and they showed significantly different orientation tuning across the range of spatial frequencies. The results are discussed with reference to previous determinations of orientation specificity, and to related psychophysical and neurophysiological phenomena.

Spatio-Chromatic Information Content of Natural Scenes

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 162-162 ◽  
Author(s):  
T Troscianko ◽  
C A Parraga ◽  
G Brelstaff ◽  
D Carr ◽  
K Nelson
Keyword(s):  
Spatial Frequency ◽  
Human Vision ◽  
Natural Scenes ◽  
Data Set ◽  
Frequency Space ◽  
Sensitivity Functions ◽  
Visual Encoding ◽  
Spatial Frequencies ◽  
Hyper Spectral ◽  
Fourier Spectra

A common assumption in the study of the relationship between human vision and the visual environment is that human vision has developed in order to encode the incident information in an optimal manner. Such arguments have been used to support the 1/f dependence of scene content as a function of spatial frequency. In keeping with this assumption, we ask whether there are any important differences between the luminance and (r/g) chrominance Fourier spectra of natural scenes, the simple expectation being that the chrominance spectrum should be relatively richer in low spatial frequencies than the luminance spectrum, to correspond with the different shape of luminance and chrominance contrast sensitivity functions. We analysed a data set of 29 images of natural scenes (predominantly of vegetation at different distances) which were obtained with a hyper-spectral camera (measuring the scene through a set of 31 wavelength bands in the range 400 – 700 nm). The images were transformed to the three Smith — Pokorny cone fundamentals, and further transformed into ‘luminance’ (r+g) and ‘chrominance’ (r-g) images, with various assumptions being made about the relative weighting of the r and g components, and the form of the chrominance response. We then analysed the Fourier spectra of these images using logarithmic intervals in spatial frequency space. This allowed a determination of the total energy within each Fourier band for each of the luminance and chrominance representations. The results strongly indicate that, for the set of scenes studied here, there was no evidence of a predominance of low-spatial-frequency chrominance information. Two classes of explanation are possible: (a) that raw Fourier content may not be the main organising principle determining visual encoding of colour, and/or (b) that our scenes were atypical of what may have driven visual evolution. We present arguments in favour of both of these propositions.

Cortical processing of second-order motion

1999 ◽  
Vol 16 (3) ◽  
pp. 527-540 ◽  
Author(s):  
ISABELLE MARESCHAL ◽  
CURTIS L. BAKER
Keyword(s):  
Spatial Frequency ◽  
High Spatial Frequency ◽  
Second Order ◽  
Spatial Properties ◽  
Processing Stream ◽  
Spatial Frequencies ◽  
Nonlinear Input ◽  
Nonlinear Processing ◽  
Frequency Components ◽  
Optimal Values

Neurons in the mammalian visual cortex have been found to respond to second-order features which are not defined by changes in luminance over the retina (Albright, 1992; Zhou & Baker, 1993, 1994, 1996; Mareschal & Baker, 1998a,b). The detection of these stimuli is most often accounted for by a separate nonlinear processing stream, acting in parallel to the linear stream in the visual system. Here we examine the two-dimensional spatial properties of these nonlinear neurons in area 18 using envelope stimuli, which consist of a high spatial-frequency carrier whose contrast is modulated by a low spatial-frequency envelope. These stimuli would fail to elicit a response in a conventional linear neuron because they are designed to contain no spatial-frequency components overlapping the neuron's luminance defined passband. We measured neurons' responses to these stimuli as a function of both the relative spatial frequencies and relative orientations of the carrier and envelope. Neurons' responses to envelope stimuli were narrowband to the carrier spatial frequency, with optimal values ranging from 8- to 30-fold higher than the envelope spatial frequencies. Neurons' responses to the envelope stimuli were strongly dependent on the orientation of the envelope and less so on the orientation of the carrier. Although the selectivity to the carrier orientation was broader, neurons' responses were clearly tuned, suggesting that the source of nonlinear input is cortical. There was no fixed relationship between the optimal carrier and envelope spatial frequencies or orientations, such that nonlinear neurons responding to these stimuli could perhaps respond to a variety of stimuli defined by changes in scale or orientation.

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.

scholarly journals Training for object recognition with increasing spatial frequency: A comparison of deep learning with human vision

2021 ◽  
Author(s):  
Lev Kiar Avberšek ◽  
Astrid Zeman ◽  
Hans P. Op de Beeck
Keyword(s):  
Spatial Frequency ◽  
Poor Performance ◽  
Visual Input ◽  
Human Vision ◽  
Striking Similarity ◽  
Deep Convolutional Neural Networks ◽  
Frequency Information ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Coarse To Fine

AbstractThe ontogenetic development of human vision, and the real-time neural processing of visual input, both exhibit a striking similarity – a sensitivity towards spatial frequencies that progress in a coarse-to-fine manner. During early human development, sensitivity for higher spatial frequencies increases with age. In adulthood, when humans receive new visual input, low spatial frequencies are typically processed first before subsequently guiding the processing of higher spatial frequencies. We investigated to what extent this coarse-to-fine progression might impact visual representations in artificial vision and compared this to adult human representations. We simulated the coarse-to-fine progression of image processing in deep convolutional neural networks (CNNs) by gradually increasing spatial frequency information during training. We compared CNN performance, after standard and coarse-to-fine training, with a wide range of datasets from behavioural and neuroimaging experiments. In contrast to humans, CNNs that are trained using the standard protocol are very insensitive to low spatial frequency information, showing very poor performance in being able to classify such object images. By training CNNs using our coarse-to-fine method, we improved the classification accuracy of CNNs from 0% to 32% on low-pass filtered images taken from the ImageNet dataset. When comparing differently trained networks on images containing full spatial frequency information, we saw no representational differences. Overall, this integration of computational, neural, and behavioural findings shows the relevance of the exposure to and processing of input with a variation in spatial frequency content for some aspects of high-level object representations.

scholarly journals Effects of Spatial Frequency Filtering Choices on the Perception of Filtered Images

Vision ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 29
Author(s):  
Sabrina Perfetto ◽  
John Wilder ◽  
Dirk B. Walther
Keyword(s):  
Spatial Frequency ◽  
Behavioral Outcomes ◽  
High Spatial Frequency ◽  
Frequency Content ◽  
Frequency Filtering ◽  
Image Content ◽  
Specific Choice ◽  
Spatial Frequencies ◽  
Spatial Frequency Filtering ◽  
Frequency Components

The early visual system is composed of spatial frequency-tuned channels that break an image into its individual frequency components. Therefore, researchers commonly filter images for spatial frequencies to arrive at conclusions about the differential importance of high versus and low spatial frequency image content. Here, we show how simple decisions about the filtering of the images, and how they are displayed on the screen, can result in drastically different behavioral outcomes. We show that jointly normalizing the contrast of the stimuli is critical in order to draw accurate conclusions about the influence of the different spatial frequencies, as images of the real world naturally have higher contrast energy at low than high spatial frequencies. Furthermore, the specific choice of filter shape can result in contradictory results about whether high or low spatial frequencies are more useful for understanding image content. Finally, we show that the manner in which the high spatial frequency content is displayed on the screen influences how recognizable an image is. Previous findings that make claims about the visual system’s use of certain spatial frequency bands should be revisited, especially if their methods sections do not make clear what filtering choices were made.

Monophasic Temporal Modulation Increases Apparent Spatial Frequency

Perception ◽  
1974 ◽  
Vol 3 (3) ◽  
pp. 337-353 ◽  
Author(s):  
V Virsu ◽  
G Nyman
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Spatial Effect ◽  
Phase Changes ◽  
Human Vision ◽  
Maximum Effect ◽  
Temporal Modulation ◽  
Flicker Fusion Frequency ◽  
Spatial Phase ◽  
Spatial Frequencies

There are three different types of flicker—monophasic, diphasic, and polyphasic—and they have different spatial consequences with gratings. Monophasic flicker does not alter the spatial phase in time, but spatial phase changes are caused by the other two types. The effects of sinusoidal monophasic flicker on the apparent spatial frequency of sinusoidal gratings were studied in the present experiments by simultaneous spatial-frequency matches. Monophasic temporal modulation increased apparent spatial frequency. The stimulus conditions for producing a maximum effect were (a) a relatively low spatial frequency, (b) a relatively high level of light adaptation, (c) an intermediate temporal frequency (4–8 Hz), and (d) an intermediate contrast. The largest apparent increases exceeded 30%. The magnitude of the spatial effect was correlated with data on temporal resolution and contrast sensitivity collected under the same conditions. The spatial effect had a high correlation with the critical flicker-fusion frequency, and the contrast-sensitivity enhancements caused by the flicker followed functions similar to those of the spatial effect when the spatial frequency and the level of adaptation were varied. We interpret the spatial effect of low-frequency monophasic flicker as evidence that there are channels for spatial frequency in human vision whose spatial tuning depends on the spatial distribution of sensitivity in the receptive fields of single neurones. Flicker at intermediate temporal frequencies decreases the functional effectiveness of centre—surround antagonism, and makes channels otherwise responsive to high spatial frequencies responsive to low spatial frequencies. As the central decoding of channel outputs can be assumed invariant, an increase in the apparent spatial frequency follows from the change of tuning properties if the channels mediate the perception of spatial frequency. An analysis of the variability of spatial frequency matches indicated that spatial frequency discrimination, if considered in relative terms, is independent of the spatial frequency, the mean luminance, and the contrast of gratings within broad ranges of variation.

Binocular Deficits Associated With Early Alternating Monocular Defocus. II. Neurophysiological Observations

2003 ◽  
Vol 90 (5) ◽  
pp. 3012-3023 ◽  
Author(s):  
Bin Zhang ◽  
Kazuki Matsuura ◽  
Takafumi Mori ◽  
Janice M. Wensveen ◽  
Ronald S. Harwerth ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Cortical Neurons ◽  
Visual Experience ◽  
Preceding Paper ◽  
Neural Signals ◽  
V1 Neurons ◽  
Sensitivity Loss ◽  
Spatial Frequencies ◽  
Frequency Components ◽  
Abnormal Visual

Experiencing binocularly conflicting signals early in life dramatically alters the binocular responses of cortical neurons. Because visual cortex is highly plastic during a critical period of development, cortical deficits resulting from early abnormal visual experience often mirror the nature of interocular decorrelation of neural signals from the two eyes. In the preceding paper, we demonstrated that monkeys that experienced early alternating monocular defocus (–1.5, –3.0, or –6.0 D) show deficits in stereopsis that generally reflected the magnitude of imposed monocular defocus. Because these results indicated that alternating monocular defocus affected the higher spatial frequency components of visual scenes more severely, we employed microelectrode recording methods to investigate whether V1 neurons in these lens-reared monkeys exhibited spatial-frequency-dependent alterations in their binocular response properties. We found that a neuron's sensitivity to interocular spatial phase disparity was reduced in the treated monkeys and that this reduction was generally more severe for units tuned to higher spatial frequencies. In the majority of the affected units, the disparity-sensitivity loss was associated with interocular differences in monocular receptive field properties. The present results suggest that the behavioral deficits in stereopsis produced by abnormal visual experience reflect at least in part the constraints imposed by alterations at the earliest stages of binocular cortical processing and support the hypothesis that the local disparity processing mechanisms in primates are spatially tuned and can be independently compromised by early abnormal visual experience.

scholarly journals Numerical Simulation on Spatial-Frequency Domain Imaging for Estimating Optical Absorption and Scattering Properties of Two-Layered Horticultural Products

2021 ◽  
Vol 11 (2) ◽  
pp. 617
Author(s):  
Dong Hu ◽  
Yuping Huang ◽  
Qiang Zhang ◽  
Lijian Yao ◽  
Zidong Yang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Property ◽  
Optical Absorption ◽  
Spatial Frequency ◽  
Estimation Accuracy ◽  
Property Estimation ◽  
Spatial Frequencies ◽  
Stepwise Method ◽  
Horticultural Products ◽  
Layered Samples

Spatial-frequency domain imaging (SFDI) is a wide-field, noncontact, and label-free imaging modality that is currently being explored as a new means for estimating optical absorption and scattering properties of two-layered turbid materials. The accuracy of SFDI for optical property estimation, however, depends on light transfer model and inverse algorithm. This study was therefore aimed at providing theoretical analyses of the diffusion model and inverse algorithm through numerical simulation, so as to evaluate the potential for estimating optical absorption and reduced scattering coefficients of two-layered horticultural products. The effect of varying optical properties on reflectance prediction was first simulated, which indicated that there is good separation in diffuse reflectance over a large range of spatial frequencies for different reduced scattering values in the top layer, whereas there is less separation in diffuse reflectance for different values of absorption in the top layer, and even less separation for optical properties in the bottom layer. To implement the nonlinear least-square method for extracting the optical properties of two-layered samples from Monte Carlo-generated reflectance, five curve fitting strategies with different constrained parameters were conducted and compared. The results confirmed that estimation accuracy improved as fewer variables were to be estimated each time. A stepwise method was thus suggested for estimating optical properties of two-layered samples. Four factors influencing optical property estimation of the top layer, which is the basis for accurately implementing the stepwise method, were investigated by generating absolute error contour maps. Finally, the relationship between light penetration depth and spatial frequency was studied. The results showed that penetration depth decreased with the increased spatial frequency and also optical properties, suggesting that appropriate selection of spatial frequencies for a stepwise method to estimate optical properties from two-layered samples provides potential for estimation accuracy improvement. This work lays a foundation for improving optical property estimation of two-layered horticultural products using SFDI.

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