• Title/Summary/Keyword: Perceived Contrast

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A Perceived Contrast Compensation Method Adaptive to Surround Luminance Variation for Mobile Phones

  • Yang, Cheng;Zhang, Jianqi;Zhao, Xiaoming
    • Journal of the Optical Society of Korea
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    • v.18 no.6
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    • pp.809-817
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    • 2014
  • The loss in contrast-discrimination ability of the human visual system under high ambient illumination level can cause image quality degradation in mobile phones. In this paper, we propose a perceived contrast compensation method by processing the original displayed image. With consideration that the perceived contrast significantly varies across the image, this method extracts the local band contrast from the original image; it then compensates these contrast components to counteract the perceived contrast degradation. Experimental results demonstrate that this method can maintain most contrast details even in high ambient illumination levels.

Determination of the Perceived Contrast Compensation Ratio for a Wide Range of Surround Luminance

  • Baek, Ye Seul;Kim, Hong-Suk;Park, Seung-Ok
    • Journal of the Optical Society of Korea
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    • v.18 no.1
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    • pp.89-94
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    • 2014
  • It is established that the perceived image contrast is affected by surround luminance. In order to get the same perceived image contrast, the optimum surround compensation ratios for those surround conditions is needed. Much research has been performed for dark, dim, and average surrounds. In this study, a wide range of surround luminance from dark up to $2087cd/m^2$ was considered. Using magnitude estimation method, the change in perceived brightness of six test stimuli was measured under seven surround conditions; dark, dim, 2 levels of average, bright, and 2 levels of over-bright surrounds. To drive the perceived image contrast from the perceived brightness, two different definitions of contrast were tested. Their calculated results were compared with the visual data of our previous work. And to conclude, the perceived contrast compensation ratios were 1:1.11:1.2 for average, dim and dark surrounds. These were close to CIECAM02 model (1:1.17:1.31). Besides, for average, bright, over-bright1 and over-bright2 surrounds the ratios 1:1.17:1.42:1.69 were determined. For intermediate or more extreme surround conditions, the compensation ratio was obtained from the linear interpolation or extrapolation.

Perceived Image Contrast under a Wide Range of Surround Luminance

  • Baek, Ye-Seul;Kim, A-Ri;Kim, Youn-Jin;Kim, Hong-Suk;Park, Seung-Ok
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.1160-1163
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    • 2009
  • Many researches showed that perceived image contrast increases as the relative surround luminance increases. However, most experiments were conducted under limited surround conditions. In this research, a psychophysical experiment was conducted to investigate the change in perceived image contrast under wide range of surround luminance up to 1820 cd/$m^2$. A large area illuminator was used as a backlight. It consists of 23 dimmable fluorescent lamps and a sheet of diffuser. The luminance could be adjusted to 7 different surround ratios: 0, 0.3, 0.56, 0.96, 2.24, 5.81, and 9.99. Results showed that perceived image contrast changes as a typical band-pass shape and the maximum contrast is found near $S_R$=1.

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Bright Surround Luminance and Perceived Image Contrast

  • Kim, A-Ri;Kim, Hong-Suk;Park, Seung-Ok;Baek, Ye-Seul;Kim, Youn-Jin
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.745-748
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    • 2008
  • The theory of Bartleson and Breneman that the perceived image contrast changes with surround luminance (the lighter surround provides higher contrast) was tested an over bright condition($8500d/m^2$). Contrarily to the Bartleson and Breneman's results, we observed the fact that perceived constrast was decreased when surround huminance increased from dark to over bright through two sets of psychophysical experiments based upon both uniform gray patches and complex color images.

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Perceived Dark Rim Artifact in First-Pass Myocardial Perfusion Magnetic Resonance Imaging Due to Visual Illusion

  • Taehoon Shin;Krishna S. Nayak
    • Korean Journal of Radiology
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    • v.21 no.4
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    • pp.462-470
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    • 2020
  • Objective: To demonstrate that human visual illusion can contribute to sub-endocardial dark rim artifact in contrast-enhanced myocardial perfusion magnetic resonance images. Materials and Methods: Numerical phantoms were generated to simulate the first-passage of contrast agent in the heart, and rendered in conventional gray scale as well as in color scale with reduced luminance variation. Cardiac perfusion images were acquired from two healthy volunteers, and were displayed by the same gray and color scales used in the numerical study. Before and after k-space windowing, the left ventricle (LV)-myocardium boarders were analyzed visually and quantitatively through intensity profiles perpendicular the boarders. Results: k-space windowing yielded monotonically decreasing signal intensity near the LV-myocardium boarder in the phantom images, as confirmed by negative finite difference values near the board ranging -1.07 to -0.14. However, the dark band still appears, which is perceived by visual illusion. Dark rim is perceived in the in-vivo images after k-space windowing that removed the quantitative signal dip, suggesting that the perceived dark rim is a visual illusion. The perceived dark rim is stronger at peak LV enhancement than the peak myocardial enhancement, due to the larger intensity difference between LV and myocardium. In both numerical phantom and in-vivo images, the illusory dark band is not visible in the color map due to reduced luminance variation. Conclusion: Visual illusion is another potential cause of dark rim artifact in contrast-enhanced myocardial perfusion MRI as demonstrated by illusory rim perceived in the absence of quantitative intensity undershoot.

A Study on Perceived Contrast Measure and Image Quality Improvement Method Based on Human Vision Models (시각 모델을 고려한 인지 대비 측정 및 영상품질 향상 방법에 관한 연구)

  • Choi, Jong Soo;Cho, Heejin
    • Journal of Korean Society for Quality Management
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    • v.44 no.3
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    • pp.527-540
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    • 2016
  • Purpose: The purpose of this study was to propose contrast metric which is based on the human visual perception and thus it can be used to improve the quality of digital images in many applications. Methods: Previous literatures are surveyed, and then the proposed method is modeled based on Human Visual System(HVS) such as multiscale property of the contrast sensitivity function (CSF), contrast constancy property (suprathreshold), color channel property. Furthermore, experiments using digital images are shown to prove the effectiveness of the method. Results: The results of this study are as follows; regarding the proposed contrast measure of complex images, it was found by experiments that HVS follows relatively well compared to the previous contrast measurement. Conclusion: This study shows the effectiveness on how to measure the contrast of complex images which follows human perception better than other methods.

The Moderating Effect of Perceived Control over Appearance in the Social Comparison Process with Advertisement Models (광고모델과의 사회적 비교과정에서 외모통제력 지각이 갖는 조정효과)

  • Lee Yoon-Jung
    • Journal of the Korean Society of Clothing and Textiles
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    • v.30 no.4 s.152
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    • pp.633-643
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    • 2006
  • When women are exposed to images of other attractive women such as media models, it is known that many go through a social comparison process and a contrast effect occurs which results in unfavorable perception and attitudes toward the self. This paper suggests women's perception of control over their appearance as one of the factors that may moderate the contrast effect of a social comparison with attractive media models. An experiment with 211 women was conducted to examine the differential effect of viewing attractive models versus non-human images on the responses of women with high/low perceived control over appearance. A two(Stimuli Type: attractive-model image vs. non-human image) by two(Perceived Control over Appearance: High vs. Low) MANCOVA model was tested with physical appearance anxiety, self-esteem, and body satisfaction as dependent variables and appearance orientation, body mass index, age, years of schooling, ethnicity, and marital status as covariates. A significant Perceived Control main effect on Physical Appearance Anxiety and Self-Esteem and a significant Stimuli Type by Perceived Control interaction effect on Physical Appearance Anxiety and Self-Esteem were found. Those who perceived high control over their appearance were more likely to have higher self-esteem and lower appearance anxiety. However, among those who saw attractive model's images, women perceived low appearance control showed less anxiety and higher body satisfaction than those perceived high appearance control.

Predicting Sustainable Personal Protective Equipment (PPE) Purchase Intention after the Pandemic: An Application of Health Belief Model

  • Zhu, Zong-Yi;Kim, Hyeon-Cheol
    • International journal of advanced smart convergence
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    • v.11 no.4
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    • pp.253-259
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    • 2022
  • This study aims to investigate the antecedent of consumer personal preventive equipment purchase behaviour by extending the HBM model after the pandemic. Pandemic related studies have focused on the effect of perceived susceptibility and perceived severity on consumer preventive behaviour, little studies have investigated the antecedents of consumer perceived risk. This study filled the gaps in the previous studies. This study tested all proposed hypotheses among users who have purchase the self-preventive behaviour. In final 253 valid data were collected through online survey for statistics analysis. This study found that consumer's health consciousness significantly impacted consumer's perceived severity of COVID-19 and perceived risk. Perceived risk positively impacted consumer self-preventive equipment purchase intention. In contrast, perceived susceptibility did not significantly consumer perceived risk. Based on these results, the theoretical implication will be offered on the study of health-related studies and will be given insight for disease control center to effectively manage consumer self-preventive behaviour.

A Study in the Perception of the Harmony of Coloration in Traditional Korean Dress of Korean and American Students (Part IV) - On the Contrast Coloration - (한복배색의 조화감에 대한 한${\cdot}$미 여대생의 지각 반응 연구 (제4보) - 콘트라스트 배색을 중심으로 -)

  • Kang Kyung-Ja;Jeong Su-Jin
    • Journal of the Korean Society of Clothing and Textiles
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    • v.29 no.6
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    • pp.825-836
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    • 2005
  • The purpose of this research is to analyze the harmony of contrast coloration of the traditional Korean dress as the subject of the study for women's college students in Korea and America. The sense of harmonious coloration for 64 colorations was evaluated based on a yellow and a green Korean jackets, to be contrast colorization, by combining four different tones, vivid, light, dull, and dark tones in a purple and a blue skirt with a yellow jacket, a red and a purple skirt with a green jacket. We tried to make sure of the cultural difference by the distinction in the perception of women's college students. in Korea and America. The result of the study is as follows. In the contrast coloration of a yellow jacket with a purple and a blue skirt, Korean women students, generally, perceived that the coloration that skirt is more dark than jacket, dull and dark tone is harmonious. On the other hand, American women students perceived harmonious skirt tone is various depending on the jacket tones. In the coloration of a green jacket and a red skirt, the women students of two countries are in common that the coloration of a vivid skirt with a vivid, a dull, and a dark jacket are harmonious. However, Korean women students indicated that a light jacket with a dark tone skirt as a harmonious coloration. American women students evaluated that various tones of coloration as a harmonious coloration. In the coloration of a green jacket and a purple skirt, Korean women students perceived that the coloration is incompatible coloration. American women students perceived the coloration is congruous in the coloration of a dull and a dark tone jacket and skirt. In the response of the perception for 64 contrast coloration, Korean students evaluated 14 sets and American students judged 28 sets as harmonized colors. Therefore, it drew the conclusion that Korean students had the sense of harmonious coloration of more narrow range than American students. There was a difference between two cultures in the standard far contrast coloration.

Perceptual Contrast based on Distribution of Brightness in CIECAM02 for Mobile Display (CIECAM02에서의 밝기 분포 기반 모바일 디스플레이의 인지적 대비)

  • Nam, Eui-Won;Kyung, Wang-Jun;Ha, Ho-Gun;Ha, Yeong-Ho
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.2
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    • pp.141-147
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    • 2015
  • The contrast of a display is generally evaluated by using the ratio of the minimum luminance to the maximum luminance of the display. However, this contrast ratio is not matched with perceived contrast because it uses only physical characteristic of display without considering human perceptual characteristics. In this paper, the proposed contrast measure that considers perceptually discriminable brightness within the range of display brightness is suggested. First, the range between the minimum and maximum brightness of display in CIECAM02 color space is calculated to measure the length of perceived brightness for the display. Next, brightness ranges which are perceptually same at each brightness level are determined by applying Weber-Fechner ratio and then, the number of brightness values within each brightness range is counted. Finally, perceptually discriminable brightness is defined as the sum of ratio between the number of brightness values in each brightness range and the perceptual contrast length of the display. In the experiments, preference test using various displays with random brightness patches is performed to evaluate perceived contrast. As a result, the proposed measure is more consistent with human perception than the previous contrast measures.