Low- and mid-spatial-frequency component measurement for aspheres

The effects of target borders on the ability of observers to resolve moving targets (Landolt Cs) under a range of conditions were examined. Contrary to reported findings with stationary targets, it was predicted that the presence of borders would improve acuity for slow-moving targets because (i) overall stimulus energy is kept relatively constant as target detail varies, and (ii) a low-spatial-frequency component is held constant as target detail varies. In an experiment in which a two-sided border (above and below the target) was used, the predicted beneficial effect of the border at slow speeds was obtained. The results are discussed in terms of practical implications for the assessment of dynamic visual acuity as well as the potential neural mechanisms underlying performance.

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Examining the role of red background in magnocellular contribution to face perception

10.7287/peerj.preprints.1295v1 ◽

2015 ◽

Cited By ~ 1

Author(s):

Bhuvanesh Awasthi ◽

Mark A Williams ◽

Jason Friedman

Keyword(s):

Spatial Frequency ◽

Face Perception ◽

Red Light ◽

Specific Property ◽

High Spatial Frequency ◽

Arm Movement ◽

Frequency Component ◽

Behavioral Evidence ◽

Movement Curvature

This study examines the role of the magnocellular system in the early stages of face perception, in particular sex categorization. Utilizing the specific property of magnocellular suppression in red light, we investigated visually guided reaching to low and high spatial frequency hybrid faces against red and grey backgrounds. The arm movement curvature measure shows that reduced response of the magnocellular pathway interferes with the low spatial frequency component of face perception. This is the first definitive behavioral evidence for magnocellular contribution to face perception.

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Examining the role of red background in magnocellular contribution to face perception

10.7287/peerj.preprints.1295 ◽

2015 ◽

Author(s):

Bhuvanesh Awasthi ◽

Mark A Williams ◽

Jason Friedman

Keyword(s):

Spatial Frequency ◽

Face Perception ◽

Red Light ◽

Specific Property ◽

High Spatial Frequency ◽

Arm Movement ◽

Frequency Component ◽

Behavioral Evidence ◽

Movement Curvature

This study examines the role of the magnocellular system in the early stages of face perception, in particular sex categorization. Utilizing the specific property of magnocellular suppression in red light, we investigated visually guided reaching to low and high spatial frequency hybrid faces against red and grey backgrounds. The arm movement curvature measure shows that reduced response of the magnocellular pathway interferes with the low spatial frequency component of face perception. This is the first definitive behavioral evidence for magnocellular contribution to face perception.

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Examining the role of red background in magnocellular contribution to face perception

PeerJ ◽

10.7717/peerj.1617 ◽

2016 ◽

Vol 4 ◽

pp. e1617 ◽

Cited By ~ 6

Author(s):

Bhuvanesh Awasthi ◽

Mark A. Williams ◽

Jason Friedman

Keyword(s):

Spatial Frequency ◽

Face Perception ◽

Red Light ◽

Specific Property ◽

High Spatial Frequency ◽

Arm Movement ◽

Frequency Component ◽

Behavioral Evidence ◽

Movement Curvature

This study examines the role of the magnocellular system in the early stages of face perception, in particular sex categorization. Utilizing the specific property of magnocellular suppression in red light, we investigated visually guided reaching to low and high spatial frequency hybrid faces against red and grey backgrounds. The arm movement curvature measure shows that reduced response of the magnocellular pathway interferes with the low spatial frequency component of face perception. This finding provides behavioral evidence for magnocellular contribution to non-emotional aspect of face perception.

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Delayed suppression shapes disparity selective responses in monkey V1

Journal of Neurophysiology ◽

10.1152/jn.00426.2013 ◽

2014 ◽

Vol 111 (9) ◽

pp. 1759-1769 ◽

Cited By ~ 9

Author(s):

Seiji Tanabe ◽

Bruce G. Cumming

Keyword(s):

Spatial Frequency ◽

Phase Difference ◽

Time Course ◽

Receptive Fields ◽

Frequency Component ◽

Noise Pattern ◽

V1 Neurons ◽

Spatial Frequencies ◽

Time Courses ◽

Suppressive Mechanism

The stereo correspondence problem poses a challenge to visual neurons because localized receptive fields potentially cause false responses. Neurons in the primary visual cortex (V1) partially resolve this problem by combining excitatory and suppressive responses to encode binocular disparity. We explored the time course of this combination in awake, monkey V1 neurons using subspace mapping of receptive fields. The stimulus was a binocular noise pattern constructed from discrete spatial frequency components. We forward correlated the firing of the V1 neuron with the occurrence of binocular presentations of each spatial frequency component. The forward correlation yielded a complete set of response time courses to every combination of spatial frequency and interocular phase difference. Some combinations produced suppressive responses. Typically, if an interocular phase difference for a given spatial frequency produced strong excitation, we saw suppression in response to the opposite interocular phase difference at lower spatial frequencies. The suppression was delayed relative to the excitation, with a median difference in latency of 7 ms. We found that the suppressive mechanism explains a well-known mismatch of monocular and binocular signals. The suppressive components increased power at low spatial frequencies in disparity tuning, whereas they reduced the monocular response to low spatial frequencies. This long-recognized mismatch of binocular and monocular signals reflects a suppressive mechanism that helps reduce the response to false matches.

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Unresolvable Pixels Contribute to Character Legibility: Another Reason Why High-Resolution Images Appear Clearer

i-Perception ◽

10.1177/2041669520981102 ◽

2020 ◽

Vol 11 (6) ◽

pp. 204166952098110

Author(s):

Madoka Ohnishi ◽

Koichi Oda

Keyword(s):

High Frequency ◽

Character Recognition ◽

Low Vision ◽

Frequency Component ◽

High Density ◽

High Frequency Component ◽

Contrast Threshold ◽

Sample Density ◽

Spatial Frequency Component ◽

Component Content

This study examined the effect of character sample density on legibility. As the spatial frequency component important for character recognition is said to be 1 to 3 cycles/letter (cpl), six dots in each direction should be sufficient to represent a character; however, some studies have reported that high-density characters are more legible. Considering that these seemingly contradictory findings could be compatible, we analyzed the frequency component of the character stimulus with adjusted sample density and found that the component content of 1 to 3 cpl increased in the high-density character. In the following three psychophysical experiments, high sample density characters tended to have lower contrast thresholds, both for normal and low vision. Furthermore, the contrast threshold with characters of each sample density was predicted from the amplitude of the 1 to 3 cpl component. Thus, while increasing the sample density improves legibility, adding a high frequency is not important in itself. The findings suggest that enhancing the frequency components important for recognizing characters by adding the high-frequency component contributes to making characters more legible.

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Determination of the Best Emulsion for the Microscopy of Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096886 ◽

1981 ◽

Vol 39 ◽

pp. 32-33

Author(s):

David A. Grano ◽

Kenneth H. Downing

Keyword(s):

Spatial Frequency ◽

Information Transfer ◽

Signal To Noise Ratio ◽

Experimental Situation ◽

Photographic Emulsion ◽

Modulation Transfer ◽

Signal To Noise ◽

Frequency Space ◽

Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

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