Background Lightness Research Articles

Point-by-point visual enhancement with spatially and spectrally tunable laser illumination.

Vision is responsible for most of the information that humans perceive of the surrounding world. Many studies attempt to enhance the visualization of the entire scene by optimizing and tuning the overall illumination spectrum. However, by using a spatially uniform illumination spectrum for the entire scene, only certain global color shifts with respect to a reference illumination spectrum can be realized, resulting in moderate visual enhancement. In this paper, a new visual enhancement method is presented that relies on a spatially variable illumination spectrum. Such an approach can target much more dedicated visual enhancements by optimizing the incident illumination spectrum to the surface reflectance at each position. First, a geometric calibration of the projector-camera system is carried out for determining the spatial mapping from the projected pixel grid to the imaged pixel grid. Secondly, the scene is segmented for implementing the visual enhancement approach. And finally, one of three visual enhancement scenarios is applied by projecting the required color image onto the considered segmented scene. The experimental results show that the visual salience of the scene or region of interest can be efficiently enhanced when our proposed method is applied to achieve colorfulness enhancement, hue tuning, and background lightness reduction.

A model to predict visual comfort for mobile displays

AbstractA psychophysical experiment was carried out to investigate visual comfort when reading on three mobile displays at three luminance levels (100, 250 and 500 cd/m2) at five illuminance levels (0, 10, 100, 500 and 1000 lx). Sixty observers including 20 children, 20 young people and 20 elderly people evaluated visual comfort of 42 text‐background combinations using a six‐category point's method. Various effects of lightness contrast, lightness of background, display luminance, and ambient illuminance on visual comfort for the three age groups were revealed. Most interesting, visual comfort is strongly affected by lightness contrast and different ages. A second‐order polynomial regression model is developed to predict visual comfort based on the display settings and ambient illumination at different ages. It could be a valuable tool to design or evaluate display interfaces.

Effects of Display and Ambient Illuminance on Visual Comfort for Reading on a Mobile Device

A psychophysical experiment was carried out to investigate visual comfort when reading on three OPPO Find X3s displays at three luminance levels (100, 250 and 500 cd/m2) at five illuminance levels (0, 10, 100, 500 and 1000 lx). Twenty young observers evaluated visual comfort using a 6-category points method. The results showed that observers felt most comfortable at the illuminance of 500 lx or display luminance of 500 cd/m2. There was an interaction between ambient illuminance and display luminance. High ambient light and display brightness levels provide a more pleasant visual experience. In low ambient light, however, the lower the brightness level, the more comfortable it is to see. Regarding the influence of background colour on visual comfort, the observers felt more comfortable having a grey background than white or black colour. When at dim illuminance, the background colour would have a great influence on visual comfort for negative contrast conditions, but when at higher illuminance, different background lightness levels had a great impact on visual comfort for positive contrast conditions. The above findings are very similar to the display luminance levels of 100 and 250 cd/m2.

Influence of Different Non-color Background on Tourmaline Green

On the basis of uniform color space CIE 1976 L*a*b*, using Munsell color system as a contrast system, this paper discusses the influence of different achromatic backgrounds on tourmaline green through quantitative analysis of color indexes such as lightness, chroma and hue of green tourmaline, and draws the following conclusion: in the process of achromatic background lightness transformation, the lightness and chroma of green tourmaline are highly sensitive to it and have obvious changes along with it, and the two also have high synchronization; However, the hue has not changed much. At the same time, the green tourmaline itself has higher lightness and chroma, which can make the lightness of the achromatic background more effectively converted into the visual lightness and saturation of the tourmaline, but the green tourmaline with too high or too low lightness and chroma is hardly affected by the lightness of the achromatic background. This proves that the non-color background is suitable for most tourmaline green quality evaluation.

A test of camera surveys to study fungus-animal interactions

Abstract Spores of mushroom-forming fungi are thought to be passively dispersed by wind. Studies of the spore morphology and ecological studies suggest, however, that dispersal by animals might also play a role. Since simultaneous and long-term observations of fungus-animal interactions are not feasible, we test the efficiency of time-lapse camera surveys followed by motion detection analysis. We surveyed 21 mushrooms of seven species for three days (daytime). We found mainly insects, with an average activity of 481 visits per fungal species per day. The estimated average animal size was 18 mm2. Due to the small animal size, the image quality did not allow detailed taxon identification. Animal activity on Lactarius vellereus was significantly higher than on all other species. In general, the more light-colored and larger mushrooms and species with ornamented spores showed higher activity. A test for false negatives, however, suggests that background color lightness potentially biases results. Camera surveys could thus contribute to the study of fungus-animal interactions. However, the use of higher-resolution images, 24 h survey and a reduction of the bias caused by background lightness are necessary.

Impact of Illumination Correlated Color Temperature, Background Lightness, and Painting Color Content on Color Appearance and Appreciation of Paintings

ABSTRACTLighting design for art exhibitions has a significant impact on the enjoyment and understanding of the displayed artworks. In particular, the selection of the light sources and the design of the museum space affect the visitors’ visual perceptions of the artworks and their color appearance. This project investigated some of the potential factors—the correlated color temperature (CCT) of the illumination, the overall color content of the painting and the lightness of its background—affecting a painting’s color appearance and appreciation in a museum setting. The study involved a survey conducted in the laboratory with both naïve observers and lighting experts. The CCT of the lighting was found to be the main factor affecting the painting’s appearance and the observers’ overall preference for the lighting arrangements, whereas the overall hue content of the painting and the background lightness had a minor influence. Furthermore, it has been found that the perceived brightness increases along with the CCT.

An adaptive scale Gaussian filter to explain White's illusion from the viewpoint of lightness assimilation for a large range of variation in spatial frequency of the grating and aspect ratio of the targets.

The variation between the actual and perceived lightness of a stimulus has strong dependency on its background, a phenomena commonly known as lightness induction in the literature of visual neuroscience and psychology. For instance, a gray patch may perceptually appear to be darker in a background while it looks brighter when the background is reversed. In the literature it is further reported that such variation can take place in two possible ways. In case of stimulus like the Simultaneous Brightness Contrast (SBC), the apparent lightness changes in the direction opposite to that of the background lightness, a phenomenon often referred to as lightness contrast, while in the others like neon colour spreading or checkerboard illusion it occurs opposite to that, and known as lightness assimilation. The White’s illusion is a typical one which according to many, does not completely conform to any of these two processes. This paper presents the result of quantification of the perceptual strength of the White’s illusion as a function of the width of the background square grating as well as the length of the gray patch. A linear filter model is further proposed to simulate the possible neurophysiological phenomena responsible for this particular visual experience. The model assumes that for the White’s illusion, where the edges are strong and quite a few, i.e., the spectrum is rich in high frequency components, the inhibitory surround in the classical Difference-of-Gaussians (DoG) filter gets suppressed, and the filter essentially reduces to an adaptive scale Gaussian kernel that brings about lightness assimilation. The linear filter model with a Gaussian kernel is used to simulate the White’s illusion phenomena with wide variation of spatial frequency of the background grating as well as the length of the gray patch. The appropriateness of the model is presented through simulation results, which are highly tuned to the present as well as earlier psychometric results.

Colour Appearance Modelling based on Background Lightness and Colour Stimulus Size in Displays

Colour Appearance Modelling based on Background Lightness and Colour Stimulus Size in Displays

A Study on Colour Appearance along the Variance of Colour Stimulus and Background Lightness at Peripheral Vision

A Study on Colour Appearance along the Variance of Colour Stimulus and Background Lightness at Peripheral Vision

The intensity of the background visual effect of crispening depending on background lightness

The paper presents the results of a research of the background visual effect of crispening depending on background lightness. An research on graphic reproductions with specifically designed solutions that involve the mentioned effect was conducted. Reproductions were designed through the variations of four different types of background lightness of 25%, 50%, 75% and 100% RTV (secondary stimuli), on which there are internal rectangles of lightness of 45%, 50% and 55% RTV (primary stimuli). The visual experiment was carried out through the use of the technique of simultaneous binocular harmonization with a 10 respondents. The ANOVA with repeated measures revealed statistically differences between the arithmetic means of variations in lightness for four variations of the background in all three primary stimuli. Further post-hoc analysis by Fisher identified the groups that mutually differ. The results indicate the regularities to which the effect of crispening is subjected in the selected graphic medium.

Quality evaluation of tourmaline red based on uniform color space

Based on the uniform color space $$\hbox {CIE}\,1976\hbox {L}^{{*}}\hbox {a}^{{*}}\hbox {b}^{{*}},$$ the red colors of 310 tourmalines were conducted with the research of color colorimetry. In terms of the quantitative analysis of color indexes such as lightness, chroma and color hue, we put forward the eight-class five-level systems for quality evaluation of tourmaline red by K-Means cluster analysis. The systems were sorted from superior to inferior: Fancy Vivid, Fancy Intense, Fancy Deep, Fancy and Fancy Dark. Through Fisher discriminant, the accuracy was proved to be up to 98.7%. Furthermore, we analyzed the effects of different standard light sources (D $$_{65},$$ A and CWF) on tourmaline red in detail. It was pointed out that D $$_{65}$$ could better reflect the color of non-self-luminous object, which was suitable for quality evaluation of tourmaline red. Light source A significantly improved the chroma and hue of tourmaline red for red tourmaline display. Light source CWF reduced the chroma of tourmaline red, making the hue significantly deviated from the red. Therefore, CWF was not suitable for tourmaline red lighting. Finally, the work discussed the effects of non-color background lightness and color background on tourmaline red to derive the following results: (1) in the process of non-color background lightness transformation, the lightness and chroma of tourmaline red were sensitive and changed significantly, with high synchronism; whereas, the color hue has unobvious change. The higher lightness and chroma of tourmaline red led to larger effects of non-color background lightness transformation to visual lightness and saturation. It was thus proved that the non-color background was suitable for quality evaluation of tourmaline red. (2) In the process of color background transformation, color metal alloy background has significantly higher lightness (average lightness 83.81) and chroma (average chroma 39.21) than tourmaline red, with obvious orange hue (average hue angle 74.48). Therefore, color metal alloy background significantly enhanced the lightness and chroma of tourmaline red, thus greatly contributing to quality evaluation of tourmaline red. However, color metal alloy background made orange hue obvious, namely strengthening mixed hue of non-mainstream red, which was not conducive to quality evaluation of tourmaline red. Therefore, color metal alloy background was only suitable for inlaid jewelry material or gemstone display rather than quality evaluation.

Context-dependent lightness affects perceived contrast

Perceived contrast of a grating varies with its background (or mean) luminance: of the two gratings with the same photometric contrast the one on higher luminance background appears to have higher contrast. Does perceived contrast also vary with context-dependent background lightness even when the luminance remains constant? We investigated this question using a stimulus in which two equiluminant patches (“context squares”, CSs) appear different in lightness. First we measured the lightness effect in a behavioral experiment. After ensuring that it was present for all participants, we conducted perceived contrast experiments, where participants judged the contrast of rectified incremental and decremental square-wave gratings superimposed on the CSs. For the incremental gratings participants’ settings were significantly different for the two CSs. Specifically, perceived contrast was higher when the gratings were placed on the context square that was perceived lighter. In a follow-up experiment we measured perceived contrast of rectified gratings on isolated patches that differed in luminance. The pattern of results of the two experiments was consistent, demonstrating that possibly shared mechanisms underpin the effects of background luminance and context-dependent lightness on perceived contrast.

The intensity of the simultaneous contrast effect depending on the change of background lightness

The paper explores the influence of the background effect of induction or simultaneous contrast on a specific type of media during the reproduction of a constructed design solution. The lightness of the background that surrounds the primary stimulus (rectangle) on a specifically constructed design was varied in ten ways. The intensity and direction of variations in the manifestation of lightness was determined with the help of the technique of simultaneous binocular harmonization on a certain number of respondents (10). The ANOVA analysis determined the existence of differences between arithmetic means (F = 132, 50 ; p = 0, 000), and the post-hoc analysis by Fisher classified three groups of samples: samples on which simultaneous contrast reflects more strongly (a very dark background) ; samples on which the effect is weaker (a light background) ; and samples on which the effect is manifested in the opposite direction (a very bright background).

배경의 밝기와 자극의 크기에 따른 색채 인지 비교 연구

This study, under the assumption that there may be a difference in colours recognized depending on background lightness and colour stimulus size, applied background lightness in a differential way and conducted an experiment by comparing the sizes of stimuli equivalent to and . Based on the results, by reflecting the results of this experiment as a difference in colour recognition, which may occur when the input image is converted from a large-sized screen to a mobile-sized screen, power efficiency, one of the biggest issues, can be reflected in mobile devices and may contribute to effective three-dimensional image reproduction and image quality in 3-D or hologram as well as 2-D images.

The Influences of Lightness Variation of the Non-Color Background on the Color of the Blood Amber

In this study, based on CIE L*a*b* uniform color space, the Color i5 measurement instrument was used to measure the color parameters of seven blood amber samples under the D65 illuminant. In addition, the influences of lightness variation of the non-color background on the lightness, the color saturation and the hue of the blood amber were also investigated and discussed. The results show that the lightness of the blood amber is significantly enhanced with the increased lightness of the non-color background and the blood amber with higher transparency is more sensitive to the change of the non-color background; the color saturation of the blood amber increases gradually with the raise of the lightness of the non-color background, which means that the blood amber on the high-lightness background looks more bright-colored than the one on the low-lightness background; the red color hue angle range of blood amber turns out to be diffusing with the increase of the lightness of the non-color background, which means that a slight difference of the hue can be more easily discriminated on the high-brightness background. Thus, it can be concluded that the blood amber with higher transparency is much easier to be influenced by the non-color background; and the increase of the lightness of the non-color background can lead to higher lightness, more bright-colored saturation and diffused hue angle range of the blood amber; and the blood amber is more bright-colored and the color difference can be more easily discriminated on the background with higher lightness.

The Influence of Variety Lightness of Neutral Background on Peridot’s Color Appearance

48 yellowish green peridots examined to test the color parameter under the neutral backgrounds whose lightness values are 10, 20, 30, 40, 50, 60, 70 and 80 by Color i5 tester, combing with the color parameter of peridots themselves, such as lightness values L*∈(50,60), chroma values C*∈(27,45), make the influence of different backgrounds on peridots’color appearence clear.With the help of two-factor analysis method, get that the F index of Row factor(standing for the lightness of peridots themselves): 16.61 which is greater than the its Fcrit index:1.40, and the F index of Column factor(standing for the lightness of backgrounds): 193.99 which is much greater than the Fcrit index, either, thus it shows that the peridots’color appearance is not only resulted by their onw lightness, but also by the backgrounds’. What is more, the influence of backgrounds is more significant; and comparing all samples’ chroma index fit line under different backgroud, find out peridot’s chroma index turning to be greater when the backgrounds’lightness increasing, and the influences are obvious during the samples with high chroma indexes. It is concluded that, for the peridots with medium lightness,the neutral backgrounds impact more on their color appearence than their own lightness do, and with the increase of backgrounds’lightness, peridots’lightness and chroma indexes will be higher.

Pedestrian Detection Using Frame Differential Method and Improved HOG Feature

To detect moving pedestrians in video surveillance rapidly and accurately, the pedestrian detection process is divided into two stages: motion detection stage and classification stage. In the motion detection stage motion detection is exploited to rapidly get the motion regions. By getting these interesting regions which may contain pedestrians, the regions used for next stage are greatly reduced and the whole pedestrian detection speed is improved. In the classification stage HOG features are used to classify interesting regions into pedestrian region and non-pedestrian region. In the motion detection stage, an improved frame differential method is used. The threshold changes with the pixel value changes and can adapt to the environment change, such as background difference, lightness change and motion speed. In the classification stage, an improved HOG method is used. Multi-scale HOG features are used to get better performance and Adaboost algorithm is used to train cascaded classifier for a higher detection speed. To evaluate the performance of our method, we test it on several video sequences taken from different scenes. Experiment results show that our method achieves good performance with an average over 90% detection rate. And our method can process over 20 frames per second and satisfies the demand for real-time task

Does target lightness depend on background luminance or background lightness?

Does target lightness depend on background luminance or background lightness?

無彩色における水彩効果‐墨絵効果の成立条件について‐

The watercolor effect (Pinna, Brelstaff, & Spillmann, 2001) is a new color spreading phenomenon. Pinna et al. (2001) proposed that the watercolor effect is a new Gestalt factor because it determines figure-ground organization more strongly than classical Gestalt factors. We used achroriatic watercolor patterns and varied the lightness of the background and two border lines to study the relationship between the color spreading effect and figure-ground organization. The results demonstrated (a)a bidirectional color spreading phenomenon when the background lightness was between the two border-lines' lightness, and that (b) some patterns elicit only a color spreading effect without organization of figure-ground, while others elicit only figure-ground organization without a color spreading effect.

Preprocessing to CIECAM02 input color with chromatic background

AbstractA preprocessing to CIECAM02 input color for color appearance prediction was proposed. In this study, 8640 color appearance matching pairs (NCS color charts with red, green, yellow, and blue backgrounds in a light booth and their reproductions with gray background on a CRT screen) were obtained by psychophysical experiment using the simultaneous‐binocular technique. Because only the lightness of background is included in CIECAM02, a color inducing vector based on opponent‐colors theory was introduced to preprocess CIECAM02 inputs, so that CIECAM02 may predict the corresponding color of an input color with chromatic background as well. By data fitting, a color preprocessing formula describing a relationship between the color inducing vector and the NCS chromaticness was conducted. Furthermore, the formula's performance was tested and the results showed that it was good for implementing the color appearance prediction of input colors with different chromatic backgrounds.© 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 40–46, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20287