Size, Shape, and Contrast in Detection of Targets by Daylight Vision I Data and Analytical Description^1

Lamar, E. S.; Hecht, Selig; Shlaer, Simon; Hendley, Charles D.

doi:10.1364/josa.37.000531

Cited by 67 publications

(31 citation statements)

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“…Thus, in searching for a liminal test field superimposed on a masking field, it usually is the boundary of the test that the 0 detects (Lamar et al, 1947). For a boundary to be detected, it is assumed that the excitation in the light band (plus-zone, z+) must differ by a criterion amount from the excitation in the z+ ------/ ---Q The aim of this article is to illustrate general properties of the model that obtain over wide ranges of parameters.…”

Section: Boundary Detectionmentioning

confidence: 99%

Model of visual adaptation and contrast detection

Sperling¹

1970

Perception & Psychophysics

138

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Section: Boundary Detectionmentioning

confidence: 99%

Model of visual adaptation and contrast detection

Sperling¹

1970

Perception & Psychophysics

138

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“…It has been known for some time that the shape, as well as the area, of a stimulus affects its luminance threshold. Lamar, Hecht, Shlaer, and Hendley (1947) found that only for stimuli below 100' square was a square target optimal; for larger targets, those with a more elongated shape had lower luminance thresholds. Kulikowski (1969) obtained consistent findings, also showing that complete summation occurred only for small targets.…”

Section: General Methodsmentioning

confidence: 94%

The Fraser illusion: Simple figures

Stuart

Day

1988

Perception & Psychophysics

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The Fraser illusion occurs when a line formed from a number of tilted segments itself appears tilted. Two explanations of this illusion were examined: (1) that the illusion results from lateral facilitation between orientation selective cells, and (2) that it is due to orientation being processed only at a local level. In Experiment 1, variations in the strength of the Fraser illusion and a comparable Zollner illusion, with change in the angle of inducing elements, were examined. There were no differences between the angular functions, but it was shown that in both cases assimilation occurred at angles as great as 18°and that solid figures showed weaker contrast illusions at larger angles. Experiment 2 indicated that this might be due to the different Fourier composition ofthe solid figures. Experiment 3 measured the local effects oflateral inhibition/facilitation and confirmed that facilitation did not take place. That indicates that the illusion results from the direct contribution oflocal information provided by the tilted segments to the global perception of the line. Finally, Experiment 4 showed that when the amount of background field used in the Zollner illusion was increased, it became negative at smaller angles, due to the increased contribution of lateral inhibition.The Fraser illusion was first described by James Fraser in 1908. A simple version of the illusion is shown in Figure la. In this figure, the letters of the word LIFE appear to be tilted with respect to one another. Physical measurement of this figure reveals that the apparent tilt is a powerful visual illusion. The illusion seems to be due to the influence of the tilted elements that make up the lines. The orientation of the elements somehow seems incorporated into the orientation of the letters as a whole.

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“…Under any of these circumstances, an observer in a full-track vehicle might be required to spot a target object which is only faintly visible. Since the visibility of objects depends in a large part upon perceptible brightness differences between the objects and their background (16), the observer might be required to make what is essentially a near-threshold brightness difference or brightness contrast discrimination. Further, the amount of time consumed by the observer under any form of obscuration in making the target discrimination may be critical.…”

Section: Srcopendationsmentioning

confidence: 99%

Influence of Noise on the Visual Contrast Threshold

Broussard¹,

Walker²,

Roberts³

1952

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THE INFLUENCE OF NOISE ON THE VISUAL CONTRAST THRESHOLD OBJECTThis study was designed to test the relative effects of two discrete noise intensities, one high and the other moderate, on the sensitivity for perception of small light differences displayed as small, variable, bright "targets" located upon a constant and less bright 'field."The effect of noise was studied further in relation to the time required to perceive and respond to the visual "target." RESULTS AND CONCLUSIONSUnder the conditions of this experiment, the visual sensitivity threshold for low brightness differences was not significantly affected by a noise environment of 90 decibels (db-) over a two-hour period when these brightness differences were exposed for a period of.adequate duration.A noise environment of 90 db significantly increased the amouint of time required to respond to small light differences when these light differences were near the threshold for discrimination.When an adequate period of time was allowed to make discriminations, the brightness difference thresholds did not differ in absolute value as a function of prolonged noise stimulation. It may be expected from the experimental'results that reducing the exposure time of the visual simuli to be discriminated to some critical range of values would raise the visual threshold under the influence of a higher level of noise.The significant effect of high-level noise on response time to near-threshold brightness differences did not seem to be functionally related to the overall duration of exposure to the noise. It may be reasonable, from the statistical results obtained in this respect, to lean toward an immediatesensory-interaction explanation for the influence of noise i rather than toward one which requires accounting for deterioration due to progressive dulling of motivation, fatigue, and the like. SR.COPE.NDATIONSFurther research should be carried out to determine if sensitivity for faintly visible targets is significantly affected by intense noise when the time permitted for perceiving the target is varied systeatically between upper and lower limits as indicated by the present study.Effects of noise of higher intensity than that used in the present study should be investigated.

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Size, Shape, and Contrast in Detection of Targets by Daylight Vision I Data and Analytical Description^1

Cited by 67 publications

References 0 publications

Model of visual adaptation and contrast detection

Model of visual adaptation and contrast detection

The Fraser illusion: Simple figures

Influence of Noise on the Visual Contrast Threshold

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