저휘도 환경에서 태블릿 PC를 이용한 장시간 독서시 문자대비가 가독성과 피로감에 미치는 영향

유하늬(Yu, Hanui),아키타 타케시(Akita, Takeshi) 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.5

This study examines the effect of luminance contrast ratio of character on readability and visual fatigue during an hour-long reading session while using a tablet PC in ambient environments having low luminance limited to 25 cd/㎡. Experiments were conducted with four patterns of the tablet’s luminance contrast ratio of characters, namely 1:2.5, 1:4.5, 1:6.5, and 1:8.5, in low ambient luminance of 9 cd/㎡ and 25 cd/㎡. The obtained results show that the characters can be easily read at the luminance contrast ratio of character of 1:8.5 under surface luminance of 25 cd/㎡. Visual fatigue was evaluated through a subjective survey of symptoms. Physical, psychological, and visual fatigue were observed at a surface luminance of 9 cd/㎡, whereas solely visual fatigue was felt at a surface luminance of 25 cd/㎡. By assessing the physical fatigue using the value, it has been found that smaller the luminance contrast ratio of character, greater is the CFF variation rate. Furthermore, readability is poor and visual fatigue can be observed when the surface luminance is lower than the ambient luminance. However, readability can be improved by increasing the luminance contrast ratio of character to a value of 1:8.5. Thus, in low luminance environments, luminance contrast ratio of characters can affect readability and fatigue. Consider providing the full form of “CFF” so that the acronym can be used unambiguously throughout the manuscript.

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

백예슬,김홍석,박승옥 한국광학회 2014 Current Optics and Photonics Vol.18 No.1

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 2087 cd/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.

Spatial Luminance Contrast Sensitivity: Effects of Surround

김연진,김홍석 한국광학회 2010 Current Optics and Photonics Vol.14 No.2

This study examined the effects of surround luminance on the shape of the spatial luminance contrast sensitivity function (CSF). The reduction in brightness of uniform neutral patches shown on a computer controlled display screen is also assessed to explain the change of CSF shape. Consequently, a large amount of reduction in contrast sensitivity at middle spatial frequencies can be observed; however, the reduction is relatively small for low spatial frequencies. In general, the effect of surround luminance on the CSF appears similar to that of mean luminance. Reduced CSF responses result in less power of the filtered image; therefore, the stimulus should appear dimmer with a higher surround luminance.

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

Cheng Yang,Jianqi Zhang,Xiaoming Zhao 한국광학회 2014 Current Optics and Photonics Vol.18 No.6

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.

불균일한 휘도를 갖는 창면의 불쾌글레어 평가실험

신주영(Ju-Young Shin),김정태(Jeong-Tai Kim),김원우(Won-Woo Kim) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.2

자연채광은 건물 재실자에게 시각적 편안함과 쾌적함을 제공하여 건강성을 향상시키며 조명 에너지를 절약할 수 있는 중요한 조명환경 요소이다. 자연광에 의해 발생되는 창면에서의 글레어는 장시간 노출될 시 시각의 저하, 시각적 불쾌감의 원인이 된다. 창면에 의한 불쾌글레어 평가시에는 창면에서 글레어 광원을 어떻게 선별할 것인가가 중요한 문제이다. 기존의 불쾌글레어 평가법을 적용하더라도 글레어 광원을 한정할 방법이 없다. 따라서 본 연구에 서는 글레어 광원 선별방법을 모색하기 위하여 불균일한 대광원의 휘도차가 불쾌글레어감에 미치는 영향을 검토하였다. 이를 위하여 120×120[㎝]의 정사각형 모형창을 제작하였다. 실험변수는 균일과 불균일한 휘도분포의 광원의 휘도비와 광원크기로 선정하였다. 실험방법은 모형창을 3분할한 후, 각기 다른 휘도비를 설정하여, 1[m] 1.5[m], 3[m] 거리에서 불쾌글레어를 평가하도록 하였다. 실험 결과 두 개의 결론을 얻었다. 첫째, 광원의 평균휘도가 증가 할수록 불쾌글레어 평가값이 증가하였으며, 둘째 창면 상부의 천공 부분만을 글레어 광원으로 볼 수 없으며 하부 면도 불쾌글레어 평가에 영향을 주는 것으로 나타났다. 본 연구의 결과는 채광창으로부터의 불쾌글레어 평가 시 글레어 광원을 선택하는 기준으로 활용될 수 있을 것이다. Impact of daylighting on the visual environment can improve occupant’s well-being by providing visual comfort. Also, daylighting can save energy. However, glare from window can be a direct hazard to vision and can cause serious discomfort. Selecting glare source on a window plane is very important for evaluating discomfort glare from windows. But former glare indices can not identify the range of the glare source properly. In this study, difference in glare sensation with uniform and non-uniform glare sources are evaluated to identify the range of the glare source. The glare source was assumed as 120×120[㎝] window model. The window was divided into three parts with different luminance values. The experiment was conducted under 1[m], 1.5[m], 3[m] distance from the glare source. Two results were obtained from the experiments. First, the degree of discomfort glare increased as average window luminance increased. Second, the middle and lower part of the window plane can affect evaluation of discomfort glare as well as the upper part of the window plan. These results can be used for selecting the glare source in a window with non-uniform luminance.

명소시 상태에서 휘도 감소에 따른 대비감도 변화

이은진,윤문주,김수현,양계탁,정주현,김현정,김현일,최은정 한국안광학회 2012 한국안광학회지 Vol.17 No.4

목적: 명소시 상태에서 휘도의 감소에 따른 대비감도 변화에 대하여 조사하였다. 방법: FACT 시표를 이용하여 명소시 5단계의 휘도 하에서 63명의 대학생에 대한 대비감도를 조사하였다. 결과: 측정된 대비감도는 모두 정상범위내에 있었다. 40~10 cd/m^2에서 대비감도의 정점이 6 cpd에서 3 cpd로 이동하는 것으로 관측되었고, 6 cpd와 3 cpd 에 대한 가상적인 두 대비감도 직선들의 교점으로부터 정점은 약 25 cd/m^2일때 6 cpd에서 3 cpd로 이동하는 것으로 평가되었다. 휘도가 120 cd/m^2에서 10 cd/m^2으로 감소하는 동안, 6 cpd에서 대비감도 손실이 가장 컸지만, 1.5cpd에서의 대비감도는 큰 변화가 없었다. 근사적으로 평가된 25 cd/m^2 이상의 휘도에서 대비감도는 18<12<1.5<3<6 cpd의 순으로 높았지만, 25 cd/m^2이하의 휘도에서는 18<12<1.5<6<3 cpd의 순으로 높았다. 휘도의 감소에 따른 대비감도의 손실을 대비감도 감소량 및 감소율로도 평가하였다. 대비감도 감소량은 6 cpd에서 가장 컸지만, 감소율은 18 cpd에서 가장 컸다. 결론: 본 연구에서 활용된 평가법이 대비감도 변화를 평가하는 또 다른 방법으로 활용될 수 있음을 제안한다. Purpose: To investigate changes of contrast sensitivity with decreasing luminance in photopic conditions. Methods:Contrast sensitivities for 63 university students were investigated at 5 different luminance levels using FACT chart. Results: All contrast sensitivities measured were in the normal range. The peak of contrast sensitivity function was observed to move from 6 to 3 cpd between 40 and 10 cd/m^2. From an intersection point of two hypothetical lines related with contrast sensitivity for 6 and 3 cpd, we could evaluated that the peak moved from 6 to 3 cpd at about 25 cd/m^2. When luminance decreases from 120 to 10 cd/m^2, contrast sensitivity loss at 6 cpd was most,while contrast sensitivity at 1.5 cpd changed little. We could evaluate that at luminance of more than 25 cd/m^2evaluated approximately, contrast sensitivity was high in the following order of spatial frequency: 18<12<1.5<3<6 cpd, while at luminance of less than about 25 cd/m^2 as follows: 18<12<1.5<6<3 cpd. Contrast sensitivity losses with decreasing luminance were also evaluated using the decrements and decrement rates of contrast sensitivity. The decrement of contrast sensitivity was the greatest at 6 cpd, while the decrement rate was the greatest at 8 cpd. Conclusions: We propose that evaluation methods used in this research may be available as another methods to evaluate the changes of contrast sensitivity.

휘도대비가 가독성에 미치는 영향에 대한 실험 연구 - 화면 크기와 가독량을 고려한 휘도대비 가이드라인 -

이수진,김진우,Lee, Su-Jin,Kim, Jin-Woo 대한인간공학회 2007 大韓人間工學會誌 Vol.26 No.2

The study investigates the effects of luminance contrast, which is the contrast between text color and background color, on readability in VDT environments. Our research goals are to prove that the relationship between luminance contrast and readability is not linear and to explore the best luminance contrast level for optimal readability. We conducted two pretests before the main experiment to determine the operational readability and luminance contrast levels. We also conducted a controlled main experiment, in which luminance contrast, reading amount and screen size were tested in terms of its relation with readability. The results of the main experiment indicate that the readability has a non-linear relation with luminance contrast, and the optimal readability is obtained when the contrast is equal to 0.951. Furthermore, the non-linear function and optional point stay constant regardless of screen size and reading amount. The paper ends with implications of the results that maximal contrast does not always mean the optimal readability.

사용조도와 명암비가 FPD 의 계조구분력에 미치는 영향

이종주,김상호 대한인간공학회 2006 대한인간공학회 학술대회논문집 Vol.- No.-

In this study, just noticeable differences (JND) for display luminance were estimated experimentally to evaluate the effects of ambient illumination and luminance contrast on the sensitivity of human vision. Using the Weber fractions for display luminance derived from different experimental conditions, it was calculated and compared the power of gradient differentiation of flat panel displays. Experimental results showed that luminance sensitivity of human vision is more susceptible under such a good combination between display luminance and ambient illumination. Disharmony between the two light sources can cause glare or reflections that degrade the sensitivity of human vision. Proper levels of maximum and minimum luminance for the displays relevant to given ambient light conditions can be suggested on the basis of power of gradient differentiation, which is a function of luminance sensitivity of human vision.

휘도 대비를 이용한 악천후 도로 노면표시 시인성능 평가

이석기,박원일,박기수,김용석 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.11

Visibility of pavement markings is directly related to the contrast between the luminance of markings and that of pavement. However, the current national standard uses the retro-reflective coefficient as a visibility index, but this index only covers the visibility of the markings, not the pavement. This study proposes using the luminance contrast as a visibility index. The luminance contrast corresponding to adverse weather conditions was quantitatively evaluated. The study results were a luminance contrast ratio of 8.02 in normal weather, 0.70 in foggy weather, 0.60 in rainy weather, and 0.71 in wetness after rain. The luminance of markings was 3.82 in normal weather, 1.98 in foggy weather, 3.67 in rainy weather, and 2.07 in wetness after rain. Luminance of a marking in rainy and wet conditions was lower than that of the background pavement, so it is almost impossible to achieve the functional requirement of markings. The study results show the refinement of the visibility index in the road standard to incorporate adverse weather conditions. As a further study, extended experiments need to be carried out to incorporate various marking types and weather conditions.

조도 기반 자동차 전조등 시인 성능 평가 방법의 적정성 평가

조원범 한국도로학회 2017 한국도로학회논문집 Vol.19 No.6

PURPOSES : The current practice in car headlight visibility performance evaluation is based on the luminous intensity and illuminance of headlight. Such practice can be inappropriate from a visibility point of view where visibility indicates abilities to perceive an object ahead on the road. This study aimed at evaluating the appropriateness of current headlight evaluation methodMETHODS: This study measured the luminance of object and road surface at unlit roadways. The variables were measured by vehicle type and by headlight lamp type. Based on the measurements, the distance where drivers can perceive an object ahead was calculated and then compared against such distance obtained by conventional visibility performance evaluation.RESULTS: The evaluation method based on illuminance of headlight is not appropriate when viewed from the visibility concept that is based on object-perceivable distance. Further, the results indicated a shorter object-perceiving distance even when road surface luminance is higher, thereby suggesting that illuminance of headlight and luminance of road surface are not the representative indices of nighttime visibility.CONCLUSIONS : Considering that this study utilized limited vehicle types and that road surface (background) luminance can vary depending on the characteristics of the given road surface, it would likely go too far to argue that this study’s visibility performance evaluation results can get generalized to other conditions. Regardless, there is little doubt that the current performance evaluation criterion which is based on illuminance, is unreasonable. There should be future endeavors on the current subject which will need to explore study conditions further, under which more experiments should be conducted and effective methodologies developed for evaluating automotive headlight visibility performance. Needs are recognized particularly in the development of headlight visibility performance evaluation methodology which will take into account road surface (background) luminance and luminance contrast from various perspectives as the former indicates the driver’s perception of the front road alignment and the latter being indicative of object perception performance.