Bloch's Law for Contrast Increment Detection: The Effects of Pedestal Contrast and Light Level

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 149-149
Author(s):  
R J Snowden
Keyword(s):  
Visual System ◽  
Temporal Summation ◽  
Light Level ◽  
High Light ◽  
High Contrast ◽  
Contrast Level ◽  
Low Light ◽  
Low Contrast ◽  
Temporal Characteristics ◽  
Test Grating

The duration over which contrast detection improves (Bloch's regime) decreases with increasing light level and is often thought to reflect the temporal characteristics of the visual system. There is also some evidence to suggest that the temporal characteristics of the visual system might also change with increasing contrast level (M A Georgeson, 1987 Vision Research27 765 – 780). Here we compare temporal summation for stimuli presented on a blank field or on a high contrast background. On each trial a test grating was presented for X ms with the use of a spatial-alternate forced-choice procedure. The test grating (2 cycles deg−1) was presented superimposed on a similar pedestal grating which was also present for 500 ms prior to and after the test grating. Pedestal contrasts of 0% and 32% were tested at mean luminance levels of 150 cd m−2 and 1.5 cd m−2. The results show that both increasing light level and increasing contrast level resulted in smaller temporal summation times. In the current conditions both these effects approximately halve the summation time such that for a stimulus of low light level and of low pedestal contrast the summation time was ∼60 ms; low light, high contrast ∼30 ms; high light, low contrast ∼30 ms; and high light, high contrast ∼15 ms. The results imply that the temporal response of the visual system quickens with increasing contrast.

Dynamic shifts of the contrast-response function

1997 ◽  
Vol 14 (3) ◽  
pp. 577-587 ◽  
Author(s):  
Jonathan D. Victor ◽  
Mary M. Conte ◽  
Keith P. Purpura
Keyword(s):  
Gain Control ◽  
Human Vision ◽  
High Contrast ◽  
Contrast Level ◽  
Low Contrast ◽  
Contrast Gain ◽  
Contrast Response Function ◽  
Stimuli Response ◽  
Response Phase ◽  
Contrast Response

AbstractWe recorded visual evoked potentials in response to square-wave contrast-reversal checkerboards undergoing a transition in the mean contrast level. Checkerboards were modulated at 4.22 Hz (8.45-Hz reversal rate). After each set of 16 cycles of reversals, stimulus contrast abruptly switched between a “high” contrast level (0.06 to 1.0) to a “low” contrast level (0.03 to 0.5). Higher contrasts attenuated responses to lower contrasts by up to a factor of 2 during the period immediately following the contrast change. Contrast-response functions derived from the initial second following a conditioning contrast shifted by a factor of 2–4 along the contrast axis. For low-contrast stimuli, response phase was an advancing function of the contrast level in the immediately preceding second. For high-contrast stimuli, response phase was independent of the prior contrast history. Steady stimulation for periods as long as 1 min produced only minor effects on response amplitude, and no detectable effects on response phase. These observations delineate the dynamics of a contrast gain control in human vision.

scholarly journals The locus of flicker adaptation in the migraine visual system: A dichoptic study

Cephalalgia ◽  
2012 ◽  
Vol 33 (1) ◽  
pp. 5-19 ◽  
Author(s):  
Michel Thabet ◽  
Frances Wilkinson ◽  
Hugh R Wilson ◽  
Olivera Karanovic
Keyword(s):  
Visual System ◽  
Interocular Transfer ◽  
Neural Model ◽  
Inhibitory Neurons ◽  
High Contrast ◽  
Low Contrast ◽  
Full Field ◽  
Dichoptic Viewing ◽  
High Stimulus ◽  
And Control

Background Flickering light has been shown to sensitize the migraine visual system at high stimulus contrast while elevating thresholds at low contrast. The present study employs a dichoptic psychophysical paradigm to ask whether the abnormal adaptation to flicker in migraine occurs before or after the binocular combination of inputs from the two eyes in the visual cortex. Methods Following adaptation to high contrast flicker presented to one eye only, flicker contrast increment thresholds were measured in each eye separately using dichoptic viewing. Results Modest interocular transfer of adaptation was seen in both migraine and control groups at low contrast. Sensitization at high contrast in migraine relative to control participants was seen in the adapted eye only, and an unanticipated threshold elevation occurred in the non-adapted eye. Migraineurs also showed significantly lower aversion thresholds to full field flicker than control participants, but aversion scores and increment thresholds were not correlated. Conclusions The results are simulated with a three-stage neural model of adaptation that points to strong adaptation at monocular sites prior to binocular combination, and weaker adaptation at the level of cortical binocular neurons. The sensitization at high contrast in migraine is proposed to result from stronger adaptation of inhibitory neurons, which act as a monocular normalization pool.

Influence of Light and Temperature on Bentazon Phytotoxicity to Cucumber (Cucumis sativus)

Weed Science ◽  
1983 ◽  
Vol 31 (2) ◽  
pp. 232-235 ◽  
Author(s):  
John R. Teasdale ◽  
Richard W. Thimijan
Keyword(s):  
Cucumis Sativus ◽  
Light Level ◽  
High Light ◽  
Growth Chamber ◽  
Low Light ◽  
Temperature Conditions ◽  
Chamber Studies ◽  
Growth Chamber Studies

In greenhouse and growth-chamber studies, increasing the level of either light or temperature increased bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] phytotoxicity to cucumber (Cucumis sativusL.). Light had a greater influence on phytotoxicity than did temperature. Light and temperature conditions after bentazon application had a greater influence on phytotoxicity than did light and temperature conditions before application. Maximum phytotoxicity was obtained from treatment with low light level before application and high light level after application.

Influence of automatic brightness control on the adaptation of low-light-level TV to high light

2013 ◽  
Vol 25 (10) ◽  
pp. 2582-2586
Author(s):  
郭冰涛 Guo Bingtao ◽  
王晓蕊 Wang Xiaorui ◽  
荆卫国 Jing Weiguo ◽  
王小兵 Wang Xiaobing ◽  
黄晓敏 Huang Xiaomin
Keyword(s):  
Light Level ◽  
High Light ◽  
Low Light

scholarly journals The effect of blue-blocking lenses on photostress recovery times for low and high contrast chromatic and achromatic stimuli

2019 ◽  
Author(s):  
Hind Saeed Alzahrani ◽  
Sieu K. Khuu ◽  
Adiba Ali ◽  
Maitreyee Roy
Keyword(s):  
Light Exposure ◽  
Bright Light ◽  
Light Sources ◽  
High Contrast ◽  
Night Time ◽  
Low Light ◽  
Low Contrast ◽  
Light Levels ◽  
Recovery Times ◽  
Visible Wavelengths

AbstractThe selective reduction in visible wavelengths transmitted through commercially available blue-blocking lenses (BBLs) is known to influence the appearance and contrast detection of objects, particularly at low light levels which may impact the human retinal receptor response time to dynamic light changes during phostress events. In the present study, we assessed whether BBLs selectively affect photostress recovery times (PSRTs) in 12 participants for chromatic and achromatic stimuli presented under low and high contrast luminance conditions. Four types of commercially available BBLs were evaluated, and their effects on PSRTs were investigated. Our results showed that PSRTs required to detect high contrast chromatic and achromatic stimuli were unaffected by BBLs when compared to a clear control lens. However, PSRTs were significantly affected by BBLs and were longer when chromatic and achromatic stimuli were of low contrast. In addition, BBLs had the greatest impact on the PSRTs of blue coloured targets, and this was dependent on the spectral transmittance profile. These results indicate that wearing BBLs under low contrast conditions can have serious implications for visual behavior, particularly under low-light levels and in situations in which the observer is directly exposed to bright light sources. For example, during night time driving, the driver might be briefly exposed to bright lights by glancing at the headlights of a passing car. This increases the time required for vision to be restored after bright light exposure, resulting in delayed object detection, and therefore stoppage and reaction times, which might pose a safety risk for a driver.

Optical Correlation Recognition Research of Low Light Level Target Based on Lifting Wavelet Transform

2013 ◽  
Vol 552 ◽  
pp. 529-535
Author(s):  
Qi Bo Zhang ◽  
Su Zhang ◽  
Yu Zhang ◽  
Wen Sheng Wang
Keyword(s):  
Wavelet Transform ◽  
Target Recognition ◽  
Correlation Method ◽  
Light Level ◽  
Joint Transform Correlator ◽  
Target Image ◽  
Low Light ◽  
Optical Correlation ◽  
Low Contrast ◽  
Noise Interference

Optical correlation technology is an important application in target recognition field, which can apply Joint Transform Correlator (JTC) to achieve target recognition. For the Low Light Level (LLL) target with low contrast and background noise interference, using optical correlation method may reduce the recognition ratio. In order to solve the problem, an effective algorithm-adaptive directional lifting based on wavelet transform (ADL) is used to process LLL target image. LLL image enhancement and target edge extraction are applied in this algorithm. Experimental results show that this algorithm can enhance the brightness of the correlation peaks and has the advantage of quick operation.

scholarly journals A SEC Vidicon System for Satellite Applications

1971 ◽  
Vol 41 ◽  
pp. 360-360
Author(s):  
G. E. Brückner
Keyword(s):  
Signal To Noise Ratio ◽  
Light Level ◽  
Zero Order ◽  
Signal To Noise ◽  
Compression Scheme ◽  
Low Light ◽  
Low Contrast ◽  
Satellite Applications ◽  
Theoretical Considerations

This paper describes a small, low power SEC vidicon camera developed for recording images of the outer solar corona from an OSO satellite. The SEC vidicon has been selected for this application because of its capability to integrate and store low light level and low contrast images. The achieved signal to noise ratio will be discussed and compared with theoretical considerations. A new operational method to readout the tube very slowly will be described. The influence of a zero order data compression scheme on the quality of the coronal images will be discussed.

Resistance Monitor and Control for Vacuum Evaporation of Metals and Carbon

1976 ◽  
Vol 34 ◽  
pp. 572-573
Author(s):  
Russell L. Steere ◽  
Eric F. Erbe ◽  
J. Michael Moseley
Keyword(s):  
Electronic Device ◽  
Point Sources ◽  
High Contrast ◽  
Variable Resistor ◽  
Quality Of Results ◽  
Low Contrast ◽  
Evaporation Source ◽  
And Control ◽  
At Will

We have designed and built an electronic device which compares the resistance of a defined area of vacuum evaporated material with a variable resistor. When the two resistances are matched, the device automatically disconnects the primary side of the substrate transformer and stops further evaporation.This approach to controlled evaporation in conjunction with the modified guns and evaporation source permits reliably reproducible multiple Pt shadow films from a single Pt wrapped carbon point source. The reproducibility from consecutive C point sources is also reliable. Furthermore, the device we have developed permits us to select a predetermined resistance so that low contrast high-resolution shadows, heavy high contrast shadows, or any grade in between can be selected at will. The reproducibility and quality of results are demonstrated in Figures 1-4 which represent evaporations at various settings of the variable resistor.

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