Article

Smaller pupil size and better proofreading performance with positive than with negative polarity displays

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Abstract

The 'positive polarity advantage' describes the fact that reading performance is better for dark text on light background (positive polarity) than for light text on dark background (negative polarity). We investigated the underlying mechanism by assessing pupil size and proofreading performance when reading positive and negative polarity texts. In particular, we tested the display luminance hypothesis which postulates that the typically greater brightness of positive compared to negative polarity displays leads to smaller pupil sizes and, hence, a sharper retinal image and better perception of detail. Indeed, pupil sizes were smaller and proofreading performance was better with positive than with negative polarity displays. The results are compatible with the hypothesis that the positive polarity advantage is an effect of display luminance. Limitations of the study are being discussed.

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... There are studies that have shown that greater luminance and positive polarity (dark text on light background), which reduce pupil size, lead to a sharper retinal image and better perception of details, and therefore a higher preference for these type of stimuli has been established (Buchner & Baumgartner, 2007;Piepenbrock, Mayr, Mund, & Buchner, 2013). As indicated by Piepenbrock, Mayr, and Buchner (2014), pupillary constriction would permit better reading performance, and hence, bright positive polarity displays are recommended. There are multiple factors that play an important role on the pupillary response, including light, target size and distance, apparent lateral or vertical displacement, fusional vergence, or stimulus contrast among others (Kasthurirangan & Glasser, 2006;Myers, Barez, Krenz, & Stark, 1990;Phillips, Winn, & Gilmartin, 1992;Wang & Munoz, 2014). ...
... However, we found a significant pupil size reduction with the positive polarities. The higher luminance associated with positive polarity may be the more plausible explanation to greater reading speed found with these polarities, since a greater pupillary constriction has been associated with better reading performance (Piepenbrock et al., 2014(Piepenbrock et al., , 2013. It has been stated that the greater depth of focus associated with positive polarities (smaller pupil sizes) may allow to reduce the accommodative efforts required to obtain a sharp image at near distances (López-Gil et al., 2013). ...
... In addition, a higher familiarity and experience of positive polarity text presentations could also influence reading speed (Hall & Hanna, 2004). Our findings agree with previous authors (Piepenbrock et al., 2014;Zuffi, Brambilla, & Beretta, 2009), with the Y-W text-background color combination, leading to the worst reading speed (number of words read per minute). The Y-W color combination has demonstrated to impose greater levels of cognitive effort in comparison to other color combinations, and thus, its use is discouraged (Bhattacharyya et al., 2014). ...
Article
The purpose of the present study was to assess the accommodative response and pupillary dynamics while reading passages with different text-background color combinations on an LCD screen. Twenty healthy young adults read fourteen 2-min passages designed with fourteen different color combinations between text and background, while the accommodative and pupil responses were continuously measured with a binocular open-field autorefractometer. Our results revealed that the text-background color combination modulates the accommodative and pupillary dynamics during a 2-minutes reading task. The blue-red combination induced a heightened accommodative response, whereas positive polarities were associated with more variability of the accommodative response and smaller pupil sizes. Participants reported lower perceived ratings of legibility for text-background color combination with lower luminance contrast (white-yellow). The manipulation of text-background color did not have a significant effect on reading speed. These results may have important applications in the design of digital visual interfaces.
... The relative legibility tradeoffs of negative versus positive polarity displays have garnered considerable attention in recent years. Recent research has shown that positive polarity text has superior legibility compared to negative polarity (Buchner and Baumgartner, 2007;Mayr and Buchner, 2010;Piepenbrock et al., 2013aPiepenbrock et al., , 2014Piepenbrock et al., 2013b;Saito, 1990, 1993;Tsang et al., 2012). This "positive polarity advantage", as some have termed it, has been shown to increase as text size decreases (Piepenbrock et al., 2013a), and is more pronounced for younger observers (Piepenbrock et al., 2013b). ...
... This "positive polarity advantage", as some have termed it, has been shown to increase as text size decreases (Piepenbrock et al., 2013a), and is more pronounced for younger observers (Piepenbrock et al., 2013b). Several competing theories have been put forth to explain the positive polarity advantage, which include simple familiarity effects (Hall and Hanna, 2004), a "luminance asymmetry effect", in which luminance decrements against the background are perceived as creating a greater change in luminance than increments of equal magnitude (Lu and Sperling, 2012), and the influence of spherical aberrations of the eye on visual input (Lombardo and Lombardo, 2010) Among these theories, a converging stream of evidence strongly suggests that the positive polarity advantage arises from the differing levels of illumination produced by the two display configurations (Buchner et al., 2009;Piepenbrock et al., 2014;Taptagaporn and Saito, 1990). Positive polarity displays feature a bright background and cause the pupil to contract, which in turn reduces distortions of visual input due to the aberrations of the eye. ...
... These results are strikingly consistent with an emerging body of research on the effects of contrast polarity on legibility. Several studies have found that positive polarity stimuli are more easily perceived than their negative counterparts, an effect dubbed the "positive polarity advantage" (Buchner and Baumgartner, 2007;Lu and Sperling, 2012;Piepenbrock et al., 2014;Piepenbrock et al., 2013a). Subsequent work has shown that this effect is likely the result of pupillary dilation caused by the difference in illumination between positive and negative polarity displays, or more precisely, the luminance of the large background areas in these conditions. ...
Article
Recent research on the legibility of digital displays has demonstrated a “positive polarity advantage”, in which black-on-white text configurations are more legible than their negative polarity, white-on-black counterparts. Existing research in this area suggests that the positive polarity advantage stems from the brighter illumination emitted by positive polarity displays, as opposed to the darker backgrounds of negative polarity displays. In the present study, legibility thresholds were measured under glance-like reading conditions using a lexical decision paradigm, testing two type sizes, display polarities, and ambient illuminations (near-dark and daylight-like). Results indicate that legibility thresholds, quantified as the amount of time needed to read a word accurately, were highest for the negative polarity configurations under dark ambient illumination, indicated worse performance. Conversely, the positive polarity conditions under dark ambient illumination and all conditions under bright illumination demonstrated significantly reduced thresholds, indicating greater legibility. These results are consistent with the hypothesis that the “positive polarity advantage” arises because brighter illumination produces pupillary contraction that reduces optical aberrations as light enters the eye. These results have implications for the design of automotive interfaces and other scenarios in which an interface must be optimized for glance-like reading under variations in ambient lighting conditions.
... Taken together, previous research has provided compelling evidence for an advantage of small pupils (and a bright background) for text reading (Buchner et al., 2009;Dobres et al., 2017;Piepenbrock et al., 2014bPiepenbrock et al., , 2014aTaptagaporn & Saito, 1990). There is also some neurophysiological evidence for a small-pupil benefit for visual acuity (Bombeke et al., 2016; but see Ajasse et al., 2018). ...
... Specifically, we found that small pupils (and thus a bright periphery) lead to improved discrimination of small letters presented in central vision. This is consistent with previous studies that showed a so-called positivepolarity advantage; that is, it is easier to read dark letters on a bright background (positive polarity) than it is to read bright letters on dark background (negative polarity) (Buchner et al., 2009;Dobres et al., 2017;Piepenbrock et al., 2014bPiepenbrock et al., , 2014aTaptagaporn & Saito, 1990). We observed this effect only (but highly reliably) with very small letters that were at the limits of visual acuity. ...
... Our results also have implications for the ergonomics of display design. First, as was already well-established, visual information that requires fine discrimination, such as text, is best displayed on a bright background (positive polarity), which induces small pupils (Buchner et al., 2009;Dobres et al., 2017;Piepenbrock et al., 2014bPiepenbrock et al., , 2014aTaptagaporn & Saito, 1990). Second, and this is a novel insight that results from our findings, visual information that should capture attention, such as notifications, may be best displayed on a dark background (negative polarity), which induces large pupils. ...
Preprint
Full-text available
It is easier to read dark text on a bright background (positive polarity) than to read bright text on a dark background (negative polarity). This positive-polarity advantage is often linked to pupil size: A bright background induces small pupils, which in turn increases visual acuity. Here we report that pupil size, when manipulated through peripheral brightness, has qualitatively different effects on discrimination of fine stimuli in central vision and detection of faint stimuli in peripheral vision. Small pupils lead to improved discrimination performance, consistent with the positive-polarity advantage, but only for very small stimuli that are at the threshold of visual acuity. In contrast, large pupils lead to improved detection performance. These results are likely due to two pupil-size related factors: Small pupils increase visual acuity, which improves discrimination of fine stimuli; and large pupils increase light influx, which improves detection of faint stimuli. Light scatter is likely also a contributing factor: When a display is bright, light scatter creates a diffuse veil of retinal illumination that reduces image contrast, thus impairing detection performance. We further found that pupil size was larger during the detection task than during the discrimination task, even though both tasks were equally difficult and similar in visual input; this suggests that the pupil may automatically assume an optimal size for the current task. Our results may explain why pupils dilate in response to arousal: This may reflect an increased emphasis on detection of unpredictable danger, which is crucially important in many situations that are characterized by high levels of arousal. Finally, we discuss the implications of our results for the ergonomics of display design.
... Several studies of the effects of color and/or contrast polarity have shown mixed results, with several indicating legibility benefits for positive polarity (dark on light) displays [8,11], another showing advantages for negative polarity (light on dark) displays [10], and at least one study that failed to show an effect of display color [7]. Recent research suggests that positive polarity displays provide a legibility advantage over negative polarity displays, and that this is most likely due to pupillary dilation in the presence of darker backgrounds, which provide less illumination than a light background [13][14][15]. The balance of evidence seems to suggest a legibility advantage for positive polarity digital text, consistent with early research on the legibility of printed materials [16]. ...
... Our results also suggest that positive polarity displays have a notable legibility advantage over negative polarity displays, at least in the laboratory lighting conditions studied here. Recent research in this area suggests that this advantage may stem from pupillary dilation effects [14,15,30]. In darker environments (as would be the case with a dark stimulus background), the pupil dilates over the imperfect surface of the eye, introducing sensory aberrations that hinder visual processing. ...
... display types, illumination, and polarity) on VDT users' task performance (e.g. Buchner and Baumgartner 2007;Buchner et al., 2009;Piepenbrock et al., 2014;Piepenbrock et al., 2013, Wilkinson andRobinshaw, 1987;Chan and Ng, 2012;Mayr et al., 2013;Chan et al., 2014;Takeda et al., 2001;Uetake et al., 2000). ...
... VDT task performance explains display productivity (Hall and Hanna, 2004;Oetjen and Ziefle, 2009;Piepenbrock et al., 2014). Generally, a speed-accuracy trade-off exists in human performance: promotion-focused individuals are inclined to perform tasks quickly, whereas prevention-focused individuals perform tasks accurately (Förster et al., 2003). ...
Article
This study examined the effects of display curvature (400, 600, 1200 mm, and flat), display zone (5 zones), and task duration (15 and 30 min) on legibility and visual fatigue. Each participant completed two 15-min visual search task sets at each curvature setting. The 600-mm and 1200-mm settings yielded better results than the flat setting in terms of legibility and perceived visual fatigue. Relative to the corresponding centre zone, the outermost zones of the 1200-mm and flat settings showed a decrease of 8%e37% in legibility, whereas those of the flat setting showed an increase of 26%e45% in perceived visual fatigue. Across curvatures, legibility decreased by 2%e8%, whereas perceived visual fatigue increased by 22% during the second task set. The two task sets induced an increase of 102% in the eye complaint score and a decrease of 0.3 Hz in the critical fusion frequency, both of which indicated an increase in visual fatigue. In summary, a curvature of around 600 mm, central display zones, and frequent breaks are recommended to improve legibility and reduce visual fatigue.
... Proofreading requires recognition of perceptual details as word and letter shapes in order to detect misspellings as well as text comprehension to identify grammar errors. Additionally, the proofreading task has frequently been shown to be sensitive to reading performance differences between screen and paper [15,[30][31][32] and display polarity [22,[33][34][35][36]. Furthermore, proofreading is a frequent real-life task, providing a high amount of ecological validity. ...
... The absence of pixel density effects on performance measures might also be due to insufficient sensitivity of the chosen experimental tasks (comprehension and proofreading). However, there is substantial evidence that at least the proofreading task is sensitive to variables such as display medium [15,[30][31][32] or textbackground polarity [22,[34][35][36]. Nevertheless, it is conceivable that an even more sensitive measure would have been able to reveal small differences of screen density. ...
Article
Displays with low pixel densities that were common in the 1980s and 1990s were shown to impair visual performance. Display technology, especially pixel density, has tremendously improved in recent years and new technologies allow densities of 264 ppi and beyond. Two experiments were conducted to test whether there are any measurable benefits of high pixel density displays (264 ppi) over moderate pixel density displays (132 ppi). In Experiment 1, participants performed a reading comprehension task on a display with either high or low pixel density. In Experiment 2, participants’ speed and performance in a proofreading task were compared using the same displays with high and low pixel density. There were no differences in reading comprehension and reading time (Experiment 1) as well as proofreading speed and performance (Experiment 2) between a 132 ppi and a 264 ppi display. However, subjective ratings of physical discomfort revealed significantly more complaints about headache and musculoskeletal strain in the 132 ppi condition than in the 264 ppi condition (Experiment 2). Reading comprehension, reading speed, and proofreading performance are unaffected by pixel densities above 132 ppi, but reading from high-resolution screens seems to be less exhausting at least subjectively. Thus, while large performance differences cannot be expected, displays with high pixel densities (264 ppi and above) have some advantage over displays with moderate (132 ppi or lower) pixel densities.
... display types, illumination, and polarity) on VDT users' task performance (e.g. Buchner and Baumgartner 2007;Buchner et al., 2009;Piepenbrock et al., 2014;Piepenbrock et al., 2013, Wilkinson andRobinshaw, 1987;Chan and Ng, 2012;Mayr et al., 2013;Chan et al., 2014;Takeda et al., 2001;Uetake et al., 2000). ...
... VDT task performance explains display productivity (Hall and Hanna, 2004;Oetjen and Ziefle, 2009;Piepenbrock et al., 2014). Generally, a speed-accuracy trade-off exists in human performance: promotion-focused individuals are inclined to perform tasks quickly, whereas prevention-focused individuals perform tasks accurately (Förster et al., 2003). ...
Article
This study examined the effects of display curvature and task duration on proofreading performance, visual discomfort, visual fatigue, mental workload, and user satisfaction. Five 27″ rear-screen mock-ups with distinct curvature radii (600R, 1140R, 2000R, 4000R, and flat) were used. Ten individuals per display curvature completed a series of four 15 min comparison-proofreading trials at a 600 mm viewing distance. Only proofreading speed benefited from display curvature, with 600R providing the highest mean proofreading speed. Proofreading speed increased and accuracy decreased for all display curvatures over the 1 h proofreading period. Visual discomfort, visual fatigue, and mental workload increased during the first 15 min of proofreading. A decrease in critical fusion frequency during that period indicated increases in visual fatigue and mental workload. A short break between 15 min proofreading tasks could be considered to prevent further degradation of task performance and ocular health.
... In certain conditions where both luminance and colour were less effective and conspicuous such as when colour discrimination was inhibited in low light environments, contrast polarity might contribute to visual response enhancement. Collectively, contrast polarity is one aspect of reading in evaluation on visual performance that has been studied in some detail (Buchner & Baumgartner, 2007;Piepenbrock et al., 2014;Piepenbrock et al., 2013). However, previous studies on polarity and contrast only had small sample sizes, so it was difficult to draw definite conclusions (Humar et al., 2008(Humar et al., , 2014Westheimer, 2003;Westheimer et al., 2003). ...
... However, the findings of the current study contradict the previous research that has found positive polarity is more advantageous than the negative polarity (Buchner & Baumgartner, 2007;Piepenbrock et al., 2014Piepenbrock et al., , 2013. The task required in proofreading performance might explain the difference in findings. ...
Article
Full-text available
Our study aimed to explore the effect of positive and negative polarities on visual acuity measurements by utilizing black and white as a text against background with three distinct colours. Visual acuity was recorded as logarithm of minimum angle of resolution (LogMAR) using the detection of the gap in a four-position Landolt-C. The 2x3 (polarity x background color) two way repeated measures ANOVA showed a statistically significant interaction between polarity and colour background on visual resolution [F (2, 16) = 23.704, p < 0.001, η2 = 0.744]. Among the three primary background colour, shorter-wavelength (blue background) showed statistically significant findings between both positive and negative polarity [F (1, 9) = 39.875, p < 0.001, η2 = 0.818]. Visual acuity measurements improved with negative polarity but decreased with positive polarity with blue colour background. However, visual acuity was not statistically significantly different with the green (medium-wavelength) [F (1, 11) = 0.625, p = 0.446, η2 = 0.053] and the red (long-wavelength) backgrounds [F (1, 9) = 4.021, p = 0.856, η2 = 0.000]. In conclusion, black text against shorter-wavelength (blue) background apparently more difficult to be resolved by human eyes compared with white text. These findings suggest colour element might be an advantage for negative polarity colour combinations.
... These optical distortions become less severe with decreasing pupil size, and this leads to measurable improvements in discrimination performance. For example, human-factors research has shown that it is easier to discriminate letters when they are presented against a bright background (Buchner et al. 2009, Dobres et al. 2017, Piepenbrock et al. 2014a); this so-called positive-polarity advantage is likely due in large part to the fact that a bright background induces small pupils (Piepenbrock et al. 2014b). ...
Article
The pupil responds reflexively to changes in brightness and focal distance to maintain the smallest pupil (and thus the highest visual acuity) that still allows sufficient light to reach the retina. The pupil also responds to a wide variety of cognitive processes, but the functions of these cognitive responses are still poorly understood. In this review, I propose that cognitive pupil responses, like their reflexive counterparts, serve to optimize vision. Specifically, an emphasis on central vision over peripheral vision results in pupil constriction, and this likely reflects the fact that central vision benefits most from the increased visual acuity provided by small pupils. Furthermore, an intention to act with a bright stimulus results in preparatory pupil constriction, which allows the pupil to respond quickly when that bright stimulus is subsequently brought into view. More generally, cognitively driven pupil responses are likely a form of sensory tuning: a subtle adjustment of the eyes to optimize their properties for the current situation and the immediate future. Expected final online publication date for the Annual Review of Vision Science, Volume 6 is September 15, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... So, many researchers work to reduce body fatigue and improve eye performance. Several researchers have determined that positive display polarity has advantageous affects for small texts and small pupils [3]. For instance, a proofreading task is controlled under the positive polarity and negative polarity [4]. ...
Article
Full-text available
Fatigue is factor which can cause health problems and decrease work efficiency. State of the art fatigue studies are mainly committed to investigating impacts of the Visual Display Terminal (VDT) screen luminance, resolution, and the distance between the VDT and operators. Fewer studies commit to understanding visual performance experienced by the operator when facing different conditions. This paper aims to find out whether the degree of fatigue and color combination of the interface that can influence visual performance when interacting with a text-based and eye tracking under exercise and no-exercise consideration. The viewing performance of 30 subjects was estimated by comparing eye tracker measurements before and after moderate exercise. Visual reaction time is significantly affected by color backgrounds. Color background transfer results in a long reaction time, while the white background transfer leads to a short time reaction time. The testers who exercise before the experiment have more positive performance than those who do not in an attention test. For the subjects who exercised, the longer they were able to rest, the better their performance. Therefore, engaging in appropriate exercise may have a good effect on the performance of operators. Additionally, the change in interface motivates eye movements and improves eye performance.
... Finally, it should be noted that the inversion of the gray scale, also called positive polarity, improves the reading comfort of tomosynthesis images due to the fact that bone and high contrast objects are almost the only structure to be analyzed. However, it is not expected to enhance its diagnostic value [25][26][27][28]. ...
Article
Tomosynthesis is an imaging technique that uses standard X-ray equipment with digital flat panel detectors to create tomographic images from very low-dose projections obtained at different angles. These images are parallel to the plane of the detector. Filtered back-projection or iterative reconstruction algorithms can be used to produce them. Iterative reconstruction used with a metal artifact reduction algorithm reduces metal artifacts, and therefore, improve image quality and in-depth spatial resolution. The radiation dose is lower compared to that of computed tomography and is two to three times the dose of a standard radiography. Tomosynthesis is intended for the analysis of high-contrast structures and especially for bones. It is superior to projection radiography when bone superimpositions are important or when metal structures hide regions of interest. The high in-plane resolution and its ability to perform exams in weight-bearing positioning are some of the main advantages of this technique. The impossible production of perpendicular multiplanar reconstruction and a limited contrast resolution are its main limitations. Tomosynthesis must be considered as an extension or an addition to standard radiography, as it can be performed in the same diagnostic step. The purpose of this article was to describe the principles, advantages and limitations, and current and future applications in musculoskeletal pathology of tomosynthesis.
... Since WYSIWYG-What You See Is What You Get-UI paradigm became the norm in editing software, light mode UIs on electronic displays, which can mimic the appearance of finished product like ink on paper, have been dominantly used and showed some benefits in user experience, such as increased visual acuity and task performance in reading [PMMB13,PMB14,BMB09]. However, while different types of displays are adopted in various use cases and circumstances in our modern lives, the need for context-adaptive UIs is increasing while taking user experience and human factors into account, e.g., night mode visualization in modern in-car displays and smartphones for improving visual acuity and reducing visual fatigue. ...
Poster
Full-text available
In the fields of augmented reality (AR) and virtual reality (VR), many applications involve user interfaces (UIs) to display various types of information to users. Such UIs are an important component that influences user experience and human factors in AR/VR because the users are directly facing and interacting with them to absorb the visualized information and manipulate the content. While consumer’s interests in different forms of near-eye displays, such as AR/VR head-mounted displays (HMDs),are increasing, research on the design standard for AR/VR UIs and human factors becomes more and more interesting and timely important. Although UI configurations, such as dark mode and light mode, have increased in popularity on other display types over the last several years, they have yet to make their way into AR/VR devices as built in features. This demo showcases several use cases of dark mode and light mode UIs on AR/VR HMDs, and provides general guidelines for when they should be used to provide perceptual benefits to the user.
... Rather, research in this area suggests that the effect has more to do with the background colors in each condition and the amount of illumination emitted into the observer's pupil from each. Research has shown that legibility is enhanced under conditions of increased illumination, regardless of the colors used, most probably because the contraction of the pupil reduces optical distortion as light enters the eye (44)(45)(46). Even though the legibility of negative-contrast conditions appears to be superior in the lab, such an advantage must be balanced with the practical disadvantage of halation (i.e., overglow or blurring) encountered on real-world road signage during night driving. ...
Article
Older drivers represent the fastest-growing segment of the driving population. Aging is associated with well-known declines in reaction time and visual processing, and, as such, future roadway infrastructure and related design considerations will need to accommodate this population. One potential area of concern is the legibility of highway signage. FHWA recently revoked an interim approval that allowed optional use of the Clearview typeface in place of the traditional Highway Gothic typeface for signage. The legibility of the two fonts was assessed with color combinations that maximized the contrast (positive or negative) or approximated a color configuration used in highway signage. Psychophysical techniques were used to establish thresholds for the time needed to decide accurately—under glancelike reading conditions—whether a string of letters was a word, as a proxy for legibility. These thresholds were lower for Clearview (indicating superior legibility) than for Highway Gothic across all conditions. Legibility thresholds were lowest for negative-contrast conditions and highest for positive-contrast conditions, with colored highway signs roughly between the two extremes. These thresholds also increased significantly across the age range studied. The method used to investigate the legibility of signage fonts adds methodological diversity to the literature along with evidence supporting the superior legibility of the Clearview font over Highway Gothic. The results do not suggest that the Clearview typeface is the optimal solution for all signage but they do indicate that additional scientific evaluations of signage legibility are warranted in different operating contexts.
... Some previous studies have shown that reading performance is better for dark text against a light background (positive polarity) than for light text against a dark background (negative polarity). [18][19][20] However, another study showed that display polarity does not affect readability. 21 The proofreading speed and accuracy were unaffected by the display polarity. ...
... Taptagaporn and Saito observed that participants developed a smaller pupil diameter when they used a positive contrast display compared to a negative contrast display [56]. This was also later confirmed to be the case by Piepenbrock et al. [48]. A small pupil diameter is known to increase the quality of the retinal image with greater depth of field and less spherical aberration, and it is largely affected by the amount of light reaching the observer's eyes. ...
Article
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Light-on-dark color schemes, so-called “Dark Mode,” are becoming more and more popular over a wide range of display technologies and application fields. Many people who have to look at computer screens for hours at a time, such as computer programmers and computer graphics artists, indicate a preference for switching colors on a computer screen from dark text on a light background to light text on a dark background due to perceived advantages related to visual comfort and acuity, specifically when working in low-light environments. In this article, we investigate the effects of dark mode color schemes in the field of optical see-through head-mounted displays (OST-HMDs), where the characteristic “additive” light model implies that bright graphics are visible but dark graphics are transparent . We describe two human-subject studies in which we evaluated a normal and inverted color mode in front of different physical backgrounds and different lighting conditions. Our results indicate that dark mode graphics displayed on the HoloLens have significant benefits for visual acuity and usability, while user preferences depend largely on the lighting in the physical environment. We discuss the implications of these effects on user interfaces and applications.
Article
Full-text available
It is easier to read dark text on a bright background (positive polarity) than to read bright text on a dark background (negative polarity). This positive-polarity advantage is often linked to pupil size: A bright background induces small pupils, which in turn increases visual acuity. Here we report that pupil size, when manipulated through peripheral brightness, has qualitatively different effects on discrimination of fine stimuli in central vision and detection of faint stimuli in peripheral vision. Small pupils are associated with improved discrimination performance, consistent with the positive-polarity advantage, but only for very small stimuli that are at the threshold of visual acuity. In contrast, large pupils are associated with improved detection performance. These results are likely due to two pupil-size related factors: Small pupils increase visual acuity, which improves discrimination of fine stimuli; and large pupils increase light influx, which improves detection of faint stimuli. Light scatter is likely also a contributing factor: When a display is bright, light scatter creates a diffuse veil of retinal illumination that reduces perceived image contrast, thus impairing detection performance. We further found that pupil size was larger during the detection task than during the discrimination task, even though both tasks were equally difficult and similar in visual input; this suggests that the pupil may automatically assume an optimal size for the current task. Our results may explain why pupils dilate in response to arousal: This may reflect an increased emphasis on detection of unpredictable danger, which is crucially important in many situations that are characterized by high levels of arousal. Finally, we discuss the implications of our results for the ergonomics of display design.
Preprint
Readability is on the cusp of a revolution. Fixed text is becoming fluid as a proliferation of digital reading devices rewrite what a document can do. As past constraints make way for more flexible opportunities, there is great need to understand how reading formats can be tuned to the situation and the individual. We aim to provide a firm foundation for readability research, a comprehensive framework for modern, multi-disciplinary readability research. Readability refers to aspects of visual information design which impact information flow from the page to the reader. Readability can be enhanced by changes to the set of typographical characteristics of a text. These aspects can be modified on-demand, instantly improving the ease with which a reader can process and derive meaning from text. We call on a multi-disciplinary research community to take up these challenges to elevate reading outcomes and provide the tools to do so effectively.
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Purpose The increasing use of online resources in emergency medicine (EM) education has driven demand for higher quality resources. Learning experience design (LED) is the study of how electronic user interfaces impact learner outcomes. We sought to summarize the evidence for LED principles to inform creation of EM educational resources. Methods We performed scripted searches of MeSH terms, Pubmed keywords, and hand tracings. Inclusion criteria were controlled studies using light‐emitting diode or liquid crystal display monitors with Latin‐based languages. Cathode ray tube (CRT) monitors were excluded because of the user experience confounders. Results 32 articles met inclusion criteria. Overall, 14‐point size significantly improved legibility compared to smaller font sizes. Similarly, Verdana and Arial typefaces significantly improved legibility compared to Times New Roman typeface. Verdana also significantly decreased subjective mental workload and visibility difficulty ratings and required the least eye movement of any typefaces tested. Positive polarity (dark text on light background) significantly improved reading outcomes across many measurements over negative polarity. There was higher character identification accuracy with higher luminance. Text effects (e.g., italics), interword and interletter spacing, and page presentation are among variables with mixed or minimal evidence. Conclusion LED principles significantly impacted reading and learning outcomes in laboratory settings. No studies evaluated classroom outcomes. Recommendations for electronic learning environments are 14 point font with Verdana or Arial typeface with positive polarity (dark letters on light background). We recommend increasing screen brightness slightly. EM educators may significantly improve the speed and accuracy of learning written material by espousing evidence‐based LED principles.
Article
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Purpose: To assess the changes in the accommodative response of the eye while reading a text under different contrast polarity conditions: black letters on white background (BoW condition) and white letters on black background (WoB condition). Methods: Eighteen subjects with ages ranging from 21 to 41 years participated in this experimental study. The accommodative response (AR) of the eye while reading a text with BoW or WoB contrast polarity was obtained objectively with an adaptive optics system that corrected all aberrations but subject's own. Two different letter sizes (visual acuity conditions), shown on a microdisplay, were tested. The AR of each eye was measured with its natural pupil diameter at 0-3D of accommodative demand from the far point of the eye, with a step of 0.5D. The slope of the stimulus-response curve was calculated for each subject and condition. Results: The averaged maximum pupil size was bigger for reverse (WoB) than for normal (BoW) contrast with statistical significance. The slopes for the ARs of the four conditions were not significantly different from each other. Conclusions: Contrast polarity does not seem to influence the accommodative response when reading text from an electronic microdisplay.
Conference Paper
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La digitalización nos lleva a estar más horas delante de las pantallas, y por ello, el impacto que tiene en la salud es foco de investigación en la actualidad. En este sentido, la polaridad de contraste juega un papel relevante en el diseño de las interfaces. En la literatura, hay trabajos que comparan la polaridad de contraste en pantallas digitales y obtienen resultados favorables para la polaridad de contraste positiva. Estas investigaciones sobre la legibilidad de las pantallas digitales han demostrado una "ventaja de polaridad positiva”. Sin embargo, la instrumentalidad no es el único valor en una experiencia. La calidad hedónica resulta importante cuando se habla de las experiencias y la percepción de los usuarios. El objetivo de esta investigación es conocer cuál es la percepción de los usuarios ante las interfaces en modo claro u oscuro mediante el Test de Asociación Implícita (IAT) y conocerlo en distinción del género. El test (n=141) ha consistido en dos partes: i) Medida implícita mediante IAT y ii) Medida explicita mediante un cuestionario. Los resultados muestran que el IAT permite conocer la preferencia preexistente de los participantes respecto al modo claro u oscuro, más concretamente, muestra un efecto pequeño hacia el modo claro-positivo.
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With eleven different types of stimuli that exercise a wide gamut of spatial and temporal visual processes, negative perturbations from mean luminance are found to be typically 25% more effective visually than positive perturbations of the same magnitude (range 8-67%). In Experiment 12, the magnitude of the black-white asymmetry is shown to be a saturating function of stimulus contrast. Experiment 13 shows black-white asymmetry primarily involves a nonlinearity in the visual representation of decrements. Black-white asymmetry in early visual processing produces even-harmonic distortion frequencies in all ordinary stimuli and in illusions such as the perceived asymmetry of optically perfect sine wave gratings. In stimuli intended to stimulate exclusively second-order processing in which motion or shape are defined not by luminance differences but by differences in texture contrast, the black-white asymmetry typically generates artifactual luminance (first-order) motion and shape components. Because black-white asymmetry pervades psychophysical and neurophysiological procedures that utilize spatial or temporal variations of luminance, it frequently needs to be considered in the design and evaluation of experiments that involve visual stimuli. Simple procedures to compensate for black-white asymmetry are proposed.
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This study investigated the effects of ambient illumination and screen luminance combination on character identification performance of thin film transistor liquid-crystal displays (TFT-LCD) monitors. Results showed that character identification performance was not significantly affected by ambient illumination at normal office levels. Further, the effects of ambient illumination regarding CRT use as found in previous studies may apply to TFT-LCD at normal office ambient illumination levels.Though our results showed that screen luminance combination did significantly affect character identification performance, the effect of screen luminance combination may be disregarded as the luminance combination of screen is adequate and the contrast ratio is high enough. In general, character identification performance increased with increasing background screen luminance. However, under high contrast ratio, C16L showed character identification performance lower than C8H. These results seem to indicate that character identification under relatively high ambient illumination is more affected by background luminance of the screen than contrast ratio or contrast sensitivity. Therefore, considering screen luminance combination and contrast ratio simultaneously may be more appropriate than considering contrast ratio alone.Relevance to industryThe TFT-LCD is fast becoming the most optimal choice in VDT display today. Ambient illumination and screen luminance combination are the key factors affecting character identification performance for TFT-LCD users. The results from this study may improve the visual performance for TFT-LCD users.
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Participants performed a word-non-word discrimination task within a car control display emulated on a thin film transistor liquid-crystal display (TFT-LCD). The task simulated an information read-out from a TFT-LCD-based instrument panel. Subsequently, participants performed a low-contrast object detection task that simulated the detection of objects during night-time driving. In experiment 1, words/non-words were presented black-on-white (positive polarity) or white-on-black (negative polarity). In experiments 2 and 3, display colour was additionally manipulated. A positive polarity advantage in the discrimination task was consistently observed. In contrast, positive displays interfered more than negative displays with subsequent detection. The detrimental after-effect of positive polarity displays was strong with white and blue, reduced with amber and absent with red displays. Subjective measures showed a preference for blue over red, but a slight advantage for amber over blue. Implications for TFT-LCD design are derived from the results. STATEMENT OF RELEVANCE: When using TFT-LCDs as car instrument panels, positive polarity red TFT-LCDs are very likely to lead to good instrument readability while at the same time minimising - relative to other colours - the negative effects of an illuminated display on low-contrast object detection during night-time driving.
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Positive- and negative-contrast stimuli yield the perceptions of brightness and darkness, respectively, and are processed separately by ON and OFF neural pathways. The properties of these morphologically and pharmacologically distinct subsystems were measured in humans by recording visual evoked potentials (VEPs). These electrical responses from the visual cortex were elicited by novel positive- and negative-contrast stimuli, designed to emphasize, selectively, contributions from ON and OFF pathways. Results revealed differential processing of the two types of contrast information, suggesting asymmetries in ON and OFF subsystems; OFF subsystems have finer spatial tuning and greater contrast gain than ON subsystems. These VEPs may be useful in diagnosing neurological disorders that involve primarily one subsystem.
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To investigate the effect of pupil diameter on higher order aberration in myopic eyes. One hundred and two eyes of 51 normal subjects were evaluated with the Nidek OPD-Scan. All types of aberration increased significantly with increasing pupil size (P<.001). However, optical aberrations had a less pronounced increase in C3(-1) and C3(+1) , more pronounced increase in C4(0) with pupil area increased (P<.05), 2nd coma (C5(-1) and C6(+1)) and high order astigmatism (C4(-2), C4(+2) C6(-2), C6(+2) with larger pupil diameter. Compared with the aberrations of each high order aberration at 4 mm, the average increase root mean square values were 1.54, 1.59, 1.71, and 1.87 on S3, S4, S5, and S6 respectively, with a 5-mm pupil, whereas increased root mean square values were 1.46, 1.88, 1.51, and 1.60 for a 6-mm-diameter pupil. For an equal increase of pupil size, not all Zernike polynomial coefficients induced equivalent increase of values. Coma-like aberrations increased less with pupil dilation. Spherical-like aberration showed only a small increase from 4 mm to 5 mm pupil size, but a larger increase from 5 mm to 6 mm pupil size. Other higher order aberrations (S5 and S6) increased slightly with pupil dilation. Coma-like aberration was larger than spherical aberration, and larger than other higher order aberrations for all pupil sizes.
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Objective: To test the display luminance hypothesis of the positive polarity advantage and gain insights for display design, the joint effects of display polarity and character size were assessed with a proofreading task Background: Studies have shown that dark characters on light background (positive polarity) lead to better legibility than do light characters on dark background (negative polarity), presumably due to the typically higher display luminance of positive polarity presentations. Method: Participants performed a proofreading task with black text on white background or white text on black background. Texts were presented in four character sizes (8, 10, 12, and 14 pt; corresponding to 0.22 degrees, 0.25 degrees, 0.31 degrees, and 0.34 degrees of vertical visual angle). Results: A positive polarity advantage was observed in proofreading performance. Importantly, the positive polarity advantage linearly increased with decreasing character size. Conclusion: The findings are in line with the assumption that the typically higher luminance of positive polarity displays leads to an improved perception of detail. Application: The implications seem important for the design of text on such displays as those of computers, automotive control and entertainment systems, and smartphones that are increasingly used for the consumption of text-based media and communication. The sizes of these displays are limited, and it is tempting to use small font sizes to convey as much information as possible. Especially with small font sizes, negative polarity displays should be avoided.
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G*Power (Erdfelder, Faul, & Buchner, 1996) was designed as a general stand-alone power analysis program for statistical tests commonly used in social and behavioral research. G*Power 3 is a major extension of, and improvement over, the previous versions. It runs on widely used computer platforms (i.e., Windows XP, Windows Vista, and Mac OS X 10.4) and covers many different statistical tests of the t, F, and chi2 test families. In addition, it includes power analyses for z tests and some exact tests. G*Power 3 provides improved effect size calculators and graphic options, supports both distribution-based and design-based input modes, and offers all types of power analyses in which users might be interested. Like its predecessors, G*Power 3 is free.
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Results are given for the variation in the depth-of-field with entrance pupil diameter for six subjects. The method was based on observation of a laser speckle pattern at 633 nm on the surface of a slowly rotating drum. Depth-of-field falls with pupil diameters up to ∼ 5 mm and then remains at an approximately constant value. The roles of diffraction, aberration, the Stiles-Crawford effect and of non-optical aspects of the visual system are discussed.
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In three experiments, the finding of slower reading of text from a video screen than from a book was replicated, and several possible reasons for this effect were explored. Extra time (9 s) taken to fill the screen had no significant effect on reading time in the video condition. Similarly, varying the contrast ratio of the video image and the distance between the screen and the reader had no effect on reading speed. The format used in the video condition (39 characters per line and 20 lines per page) produced slower reading than did a format typical for books (60 characters per line and 40 lines per page), but this effect alone (9.5%) could not account for the difference in reading speed between the book and video conditions (24.1%). The reduced reading speed was partly overcome by avoiding single spacing, which produced 10.9% slower reading than did double spacing in the video condition.
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We asked if retinal image quality is maximum during accommodation, or sub-optimal due to accommodative error, when subjects perform an acuity task. Subjects viewed a monochromatic (552 nm), high-contrast letter target placed at various viewing distances. Wavefront aberrations of the accommodating eye were measured near the endpoint of an acuity staircase paradigm. Refractive state, defined as the optimum target vergence for maximising retinal image quality, was computed by through-focus wavefront analysis to find the power of the virtual correcting lens that maximizes visual Strehl ratio. Despite changes in ocular aberrations and pupil size during binocular viewing, retinal image quality and visual acuity typically remain high for all target vergences. When accommodative errors lead to sub-optimal retinal image quality, acuity and measured image quality both decline. However, the effect of accommodation errors of on visual acuity are mitigated by pupillary constriction associated with accommodation and binocular convergence and also to binocular summation of dissimilar retinal image blur. Under monocular viewing conditions some subjects displayed significant accommodative lag that reduced visual performance, an effect that was exacerbated by pharmacological dilation of the pupil. Spurious measurement of accommodative error can be avoided when the image quality metric used to determine refractive state is compatible with the focusing criteria used by the visual system to control accommodation. Real focusing errors of the accommodating eye do not necessarily produce a reliably measurable loss of image quality or clinically significant loss of visual performance, probably because of increased depth-of-focus due to pupil constriction. When retinal image quality is close to maximum achievable (given the eye's higher-order aberrations), acuity is also near maximum. A combination of accommodative lag, reduced image quality, and reduced visual function may be a useful sign for diagnosing functionally-significant accommodative errors indicating the need for therapeutic intervention.
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We tested the hypothesis that pupil apodization is the basis for central pupil bias of spherical refractions in eyes with spherical aberration. We employed Fourier computational optics in which we vary spherical aberration levels, pupil size, and pupil apodization (Stiles Crawford Effect) within the pupil function, from which point spread functions and optical transfer functions were computed. Through-focus analysis determined the refractive correction that optimized retinal image quality. For a large pupil (7 mm), as spherical aberration levels increase, refractions that optimize the visual Strehl ratio mirror refractions that maximize high spatial frequency modulation in the image and both focus a near paraxial region of the pupil. These refractions are not affected by Stiles Crawford Effect apodization. Refractions that optimize low spatial frequency modulation come close to minimizing wavefront RMS, and vary with level of spherical aberration and Stiles Crawford Effect. In the presence of significant levels of spherical aberration (e.g. = 0.4 μm, 7 mm pupil), low spatial frequency refractions can induce −0.7 D myopic shift compared to high SF refraction, and refractions that maximize image contrast of a three cycle per degree square-wave grating can cause −0.75 D myopic drift relative to refractions that maximize image sharpness. Because of small depth of focus associated with high spatial frequency stimuli, the large change in dioptric power across the pupil caused by spherical aberration limits the effective aperture contributing to the image of high spatial frequencies. Thus, when imaging high spatial frequencies, spherical aberration effectively induces an annular aperture defining that portion of the pupil contributing to a well-focused image. As spherical focus is manipulated during the refraction procedure, the dimensions of the annular aperture change. Image quality is maximized when the inner radius of the induced annulus falls to zero, thus defining a circular near paraxial region of the pupil that determines refraction outcome.
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Unlabelled: The effect of display polarity on visual acuity and proofreading performance was investigated for younger and older adults. An advantage of positive polarity (dark characters on light background) over negative polarity (light characters on dark background) was expected for younger adults, but the effects on older adults were ambiguous. Light scatter due to residues in the senescent lens and vitreous humour could reverse the typical advantage of positive polarity. However, age-related changes lead to a decline in retinal illuminance. Brighter positive polarity displays should help to compensate for this decline and, accordingly, lead to better performance than darker negative polarity displays. Participants conducted a visual acuity test with black optotypes on white background or white optotypes on black background and performed a proofreading task in the same polarity. A positive polarity advantage was found for both age groups. The presentation in positive polarity is recommended for all ages. Practitioner summary: In an ageing society, age-related vision changes need to be considered when designing digital displays. Visual acuity testing and a proofreading task revealed a positive polarity advantage for younger and older adults. Dark characters on light background lead to better legibility and are strongly recommended independent of observer's age.
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Two experiments are reported which compared proof-reading performance in various VDU display formats. Experiment 1 found that displaying text one paragraph at a time improved the accuracy of performance, relative to a full screen condition, but at the expense of speed. Subjects also preferred using the paragraph format. Display contrast (positive vs negative) had no effect on performance. Experiment 2 supported the findings of Experiment 1, and found increased accuracy when text was further subdivided into sentences, but speed was again reduced. Possible explanations for the format effect are presented, and its practical implications are considered.
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This study investigated the effects of light source, ambient illuminance, character size, and interline spacing on visual performance and visual fatigue in using commercial electronic paper displays. Regarding visual performance the results showed that display type, character size, interline spacing had significant effects on search time. Electrophoretic electronic ink display had a shorter search time than chlorestic liquid crystal display. Searching time decreased as character size and interline spacing increased. Ambient illumination, display type, character size, and interline spacing had significant effects on accuracy. Accuracy was highest for 1500 lx ambient illumination. Accuracy of electrophoretic electronic ink display was greater than chlorestic liquid crystal display. Accuracy increased as character size and interline spacing increased. Regarding visual fatigue, results showed that light source and ambient illumination had non-significant effects on change of critical flicker fusion (CFF) and subjective visual fatigue. Results could be able to provide some guidelines for consumers to choose a suitable electronic paper according to lighting condition and set appropriate character size and interline spacing.Research highlights► Results showed that visual performance and visual fatigue did not depend on light source. ► E-paper could be used under various light sources. ► Some guidelines was provided for consumers to choose a suitable electronic paper according to the lighting condition (ambient illumination at 700 lx and greater ambient illumination such as 1500 lx may be even better for E-paper) and set character size at about 3.0 mm and retain appropriate interline spacing about 66% of character size. ► Better visual performance was shown for E-ink 401 display (Sony LIBRIe’) than Ch-LC display (Kolin i-library).
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The study used the simulated e-paper to investigate how the bending radius of curvature (−10 cm, plane, and 10 cm) and 12 text/background color-combinations of e-paper affect subjects’ visual performance and subjective preference under various ambient illuminance conditions (200 and 500 lx). Analysis results indicated that the bending curvature and ambient illuminance did not significantly affect subjects’ visual performance. However, subjects visual performance differed significantly for different text/background color combinations of the simulated e-paper. When the background color of the simulated e-paper was set to yellow-like condition and the luminance of the text was low (2.2 and 4.6 cd/m2), subjects’ visual performance was best. Regarding the subjective preferences of subjects, the results of this research also demonstrated that the bending curvature, text/background color combinations and ambient illuminance all significantly affected the subjective preferences of subjects. Subjects exhibited the best preference under the following settings: bending curvature of the simulated e-paper set to plane; background color of the simulated e-paper set to yellow-like condition and low text luminance (2.2 or 4.6 cd/m2); high ambient illuminance (500 lx).
Article
The effect of display polarity and luminance contrast on visual lobe (effective visual field) shape characteristics was studied using three levels of luminance contrast with combinations of positive and negative polarities. The binocular effective visual field for a detection task, with a peripherally presented target (V) embedded in a homogeneous competing background (Xs), was mapped on 24 imaginary axes passing through the fixation point. The results showed that visual lobes mapped using positive polarity were statistically larger in area, rounder and more regular in shape than those for negative polarity. The medium contrast condition lobes were more symmetric and regular than low contrast condition lobes, and lobe area and perimeter increased with increasing luminance contrast ratio. Under the interaction of positive polarity and high luminance contrast, visual lobes were found to be larger, smoother and rounder. The high level of luminance and contrast however resulted in a higher degree of visual discomfort. The results indicated that positive polarity and contrast of medium (26:1) to high (41:1) levels are possible display settings for better visual lobe characteristics and better anticipated search performance. Practitioner Summary: The effect of display polarity and luminance contrast on visual lobe shape characteristics was examined with uniform stimulus materials in this study. The results help to identify the optimum display settings for luminance contrast and display polarity to enhance lobe shape characteristics and hence search performance in industrial inspection tasks.
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This study investigated the effects of polarity and luminance contrast on visual performance and display quality by measuring the subjects’ performance on a discriminating VDT task. Subjects’ visual acuity was used to evaluate visual performance. Perceived display quality was evaluated by using the subjective evaluation of subjects. Based on his/her preference, every subject graded each combination on a 0–100 scale. Analysis of results showed that both visual acuity and subjective evaluation were not affected by polarity. However, the luminance contrast was significant for both measures. Specifically, visual acuity increased as luminance contrast increased up to 8 : 1 and then decreased once the luminance contrast was greater than 8 : 1. The subjects’ perception of display quality was consistent with the visual acuity findings.Relevant to industryPolarity and luminance contrast are two key factors that affect visual performance and display quality of VDT. The results from this study may assist in improving the display quality of VDT and the performance of VDT users.
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Cathode ray tube (CRT) display and liquid crystal display (LCD) were compared for their suitability in visual tasks. For this purpose visual performance was assessed by means of a search task carried out using both displays with different levels of ambient light. In addition, suitability was rated subjectively by users of visual display units (VDUs). Error frequency for search tasks carried out using LCD were significantly smaller when compared to error frequency for tasks at CRT. LCD gave rise to 34% less errors than did CRT. Reaction time in search task was found to be significantly shorter using LCD when tasks were carried out in darkness. Subjective rated suitability of LCD was scored twice as high as suitability of CRT. Results indicate that LCD used in this experiment may give better viewing conditions in comparison to CRT display.
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Very little is known about the effects of visual impairment on reading. We used psychophysical methods to study reading by 16 low-vision observers. Reading rates were measured for text scanned across the face of a TV monitor while varying parameters that are likely to be important in low vision: angular character size, number of characters in the field, number of dots composing each character, contrast polarity (white-on-black vs black-on-white text), and character spacing. Despite diverse pathologies and degrees of vision loss in our sample, several major generalizations emerged. There is a wide variation in peak reading rates among low-vision observers, but 64% of the variance can be accounted for by two major distinctions: intact central fields vs central-field loss and cloudy vs clear ocular media. Peak reading rates for observers with central-field loss were very low (median 25 words/minute), while peak reading rates for observers with intact central fields were at least 90 words/minute (median 130 words/minute). Most low-vision readers require magnification to obtain characters of optimal size. Sloan M acuity was a better predictor of optimal character size than Snellen acuity, accounting for 72% of the variance. Low-vision reading is similar to normal reading in several respects. For example, both show the same dependence on the number of characters in the field. Our results provide estimates of the best reading performance to be expected from low-vision observers with characteristic forms of vision loss, and the stimulus parameters necessary for optimal performance. These results will be useful in the development of clinical tests of low vision, and in the design of low-vision reading aids.
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In order to meet the goal of user comfort of information displays, visual problems of video display terminal (VDT) work were studied through the analysis of visual functions in two experiments. Eye movement analysis, in Experiment 1, revealed that VDT operators had to move their eyes 2.5 times faster than traditional clerical workers. Lens accommodation, pupil size, and subjective visual comfort were investigated in Experiment 2. A significant correlation was found between the velocity of lens accommodation and the subjective visual comfort while viewing seven different displays (r = .809). A positive‐type cathode‐ray tube (CRT), which has dark characters on a light background, was ascertained to be the most appropriate display type, while working with a liquid crystal display (LCD) was considered to be the least visually comfortable, with the lowest accommodative velocity.
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The purpose of this experiment was to examine the effect of web page text/background colour combination on readability, retention, aesthetics, and behavioural intention. One hundred and thirty-six participants studied two Web pages, one with educational content and one with commercial content, in one of four colour-combination conditions. Major findings were: (a) Colours with greater contrast ratio generally lead to greater readability; (b) colour combination did not significantly affect retention; (c) preferred colours (i.e., blues and chromatic colours) led to higher ratings of aesthetic quality and intention to purchase; and (d) ratings of aesthetic quality were significantly related to intention to purchase.
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The expansion of wavefront-sensing techniques redefined the meaning of refractive error in clinical ophthalmology. Clinical aberrometers provide detailed measurements of the eye's wavefront aberration. The distribution and contribution of each higher-order aberration to the overall wavefront aberration in the individual eye can now be accurately determined and predicted. Using corneal or ocular wavefront sensors, studies have measured the interindividual and age-related changes in the wavefront aberration in the normal population with the goal of optimizing refractive surgery outcomes for the individual. New objective optical-quality metrics would lead to better use and interpretation of newly available information on aberrations in the eye. However, the first metrics introduced, based on sets of Zernike polynomials, is not completely suitable to depict visual quality because they do not directly relate to the quality of the retinal image. Thus, several approaches to describe the real, complex optical performance of human eyes have been implemented. These include objective metrics that quantify the quality of the optical wavefront in the plane of the pupil (ie, pupil-plane metrics) and others that quantify the quality of the retinal image (ie, image-plane metrics). These metrics are derived by wavefront aberration information from the individual eye. This paper reviews the more recent knowledge of the wavefront aberration in human eyes and discusses the image-quality and optical-quality metrics and predictors that are now routinely calculated by wavefront-sensor software to describe the optical and image quality in the individual eye.
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Reading text from computer screens is better when text is printed in dark letters on light background (positive polarity) than when it is printed in light letters on dark background (negative polarity). An experiment is presented that tests whether this positive polarity advantage is due to the fact that overall display luminance is typically higher for positive than for negative polarity displays. To this end, text-background polarity and display luminance were manipulated independently. No positive polarity advantage was observed when overall display luminance of positive and negative polarity displays was equivalent. There was only an effect of display luminance, with better performance for the higher-luminance displays. This suggests that the positive polarity advantage is in fact due to the typically higher luminance of positive polarity displays. Readability of text presented on computer screens (e.g. on websites) is better when the overall display luminance level is high, as in positive polarity displays (dark letters on light background). Display polarity per se does not affect readability.
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Various proposals for the function of the pupillary light reflex are discussed in quantitative terms. Two proposals are examined experimentally. It is suggested that the major purpose of pupillary constriction to light is to reduce retinal illumination and prepare the eye for a return to darkness. A mobile pupil (as opposed to a fixed) produces a substantial improvement in stimulus detection during the first few minutes of dark adaptation.
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Resolution to square-wave gratings was measured over a wide range of luminance levels, and a range of size of artificial pupil. Four contrast levels of stimulus were used. The optimum pupil (highest resolution) was found to be close to the size of the natural pupil, at all contrast levels. The consequences of a fixed small or fixed dilated pupil are discussed. The loss of resolution due to a fixed dilated pupil at high light levels is found to be small.
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When the pupil is opened to increase sensitivity there is a loss of image sharpness due to aberrations. This trade-off between sensitivity and sharpness is analysed theoretically by calculating the information capacity of the retinal image. The analysis uses optical measurements of image sharpness made at different pupil diameters. At each luminance there is a pupil diameter that maximizes information capacity. This optimum is close to the diameter adopted under normal viewing conditions. The optimum is broad, consequently the system tolerates inaccurate adjustment. The benefits of correctly adjusting the pupil are evaluated. At low light levels the advantage is 68%, at intermediate levels it falls to around 20% but under daylight conditions it increases to 52%. These advantages suggest that the primary function of the pupillary light reflex is to maximize acuity over a wide range of luminances.
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This study examined legibility performance and subjective preference for text/background color combinations displayed on a video monitor. Luminance contrast was fixed at two preoptimized levels, either with text brighter than the background (10:1) or vice versa (1:6.5). In Experiment 1, 32 subjects rated about 800 color combinations. No evidence suggested differential effects of luminance polarity or hue, with the only exception that cool background colors (blue and bluish cyan) tended to be preferred for the light-on-dark polarity. Saturation had the most important influence on ratings. Any desaturated color combination appears to be satisfactory for text presentation. In Experiment 2 a reduced set of 18 color combinations was investigated with a new sample of 18 subjects. Reading and search times as well as multidimensional ratings were evaluated. There was no evidence for an influence of luminance polarity or chromaticity on performance. Subjective ratings corresponded well with the results of Experiment 1.
Article
This study ascertained that CRTs using a positive display polarity (dark characters on bright background) are ergonomically more appropriate for VDT operators than ones using a negative display polarity (bright characters on dark background), using both physiological and psychological indices. Differences of pupil size and subjective evaluation of visual comfort while undertaking visual tasks were examined for six experimental conditions (two CRT display types in three different illuminated levels). Pupil diameter was not affected greatly when working with the positive display for different illumination levels. The positive display also caused smaller differences in pupil diameter when viewing visual targets, namely CRT display, script, and keyboard, for all lighting conditions. The majority of the subjects also appreciated working with the positive CRT display at a regular office illumination level.
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People read more slowly from CRT displays than from paper (see, for example, Gould and Grischkowsky, 1984). This report summarizes ten experiments and several more analyses that seek to explain the cause of this reading-speed difference. Typically, each experiment isolates one variable and studies whether it explains the difference. Results show that no one variable studied (e.g., experience in using CRT displays; display orientation; character size, font, or polarity) explains it. The tentative conclusion is that the difference is due to a combination of variables, probably centering on the image quality of the characters themselves.
Article
How does contrast affect reading rate? What is the role of contrast sensitivity? We measured reading rate as a function of the contrast and character size of text for subjects with normal vision. Reading rates were highest (about 350 words/min) for letters ranging in size from 0.25 degree to 2 degrees. Within this range, reading was very tolerant to contrast reduction--for 1 degree letters, reading rate decreased by less than a factor of two for a tenfold reduction in contrast. The results were very similar for white-on-black and black-on-white text. Reading rate declined more rapidly for very small (less than 0.25 degree) and very large (greater than 2 degrees) letters. People with low vision usually require large characters to read, so high contrast is particularly important for them. Taking 35 words/min to be a threshold for reading, we constructed a contrast-sensitivity function (CSF) for reading. We were able to relate the shape of this CSF to the shape of sine-wave grating CSFs.
Article
Subjects read continuous text for 80 min using microfiche and video display terminals (VDTs) with negative- and positive-appearing images and printed paper copy. Measurements of visual fatigue (ocular discomfort) and reading speed were obtained periodically, and a test of reading comprehension was given at the end of each session. Visual fatigue was significantly greater when subjects read from negative microfiche (light characters, dark background) projected on a metal screen or from the screen of a VDT with positive-appearing images (dark characters, light background). However, when subjects read from microfiche projected on a high-reflectance matte screen or from the screen of a VDT with negative images, visual fatigue was not significantly greater than that reported for the printed materials. Reading speeds tended to be slower for the negative image conditions. but reading comprehension scores were similar for all conditions.
Article
This paper is about the visual requirements for reading with normal vision. It is the first in a series devoted to the psychophysics of reading with normal and low vision. We have measured reading rates for text scanned across the face of a TV monitor while varying parameters that are important in current theories of pattern vision. Our results provide estimates of the stimulus parameters required for optimal reading of scanned text. We have found that maximum reading rates are achieved for characters subtending 0.3 degree to 2 degrees. Contrast polarity (black-on-white vs white-on-black text) has no effect. Reading rate increases with field size, but only up to 4 characters, independent of character size. When text is low-pass spatial-frequency filtered, reading rate increases with bandwidth, but only up to two cycles/character, independent of character size. When text is matrix sampled, reading rate increases with sample density, but only up to a critical sample density which depends on character size. The critical sample density increases from about 4 X 4 samples/character for 0.1 degree characters to more than 20 X 20 samples/character for 24 degrees characters. We suggest that one spatial-frequency channel suffices for reading.
Article
1. Optical quality of the eye was measured at eight pupil sizes between 1.5 and 6.6 mm diameter by recording the faint light emerging from the eye; this light was reflected from the bright image of a thin line on the fundus.2. The nature of the fundus reflexion was examined; it was found that the fundus acts very much like a perfect diffuser while retaining polarization.3. Using the result that the fundus acts like a diffuser, the recorded line images were Fourier analysed to provide modulation transfer functions. These functions indicate an optical quality considerably higher than that found in previous physical studies.4. Linespread profiles were then derived from the modulation transfer functions. These profiles are 40% narrower than those of previous physical studies for a 3.0 mm pupil. The narrowest profile occurred with a 2.4 mm pupil.5. Our results demonstrate that physical and psychophysical studies can yield similar estimates of optical quality. The influence of optical factors not common to both techniques is discussed. Evidence for the existence of neural ;image sharpening' mechanisms is reviewed.
Article
We develop formulas for calculating the approximate depth of focus of any eye. They show that the magnitude of depth of focus is inversely proportional to the size of the eye and to its visual acuity. One particular implication of these quantitative relations, which is supported by previous data from rats and human infants, is that small eyes with low acuity should have large depths of focus. We show that the observed relation between defocus and contrast sensitivity in rats in predicted by our formulas. We also analyze recent findings in human infants and show that they demonstrate a good correspondence between the improvement in accuracy of the accommodative response with age and the reduction in depth of focus (predicted from our formulas) as acuity and eye size increase over the same age range. Optical factors such as astigmatism, refractive error and chromatic and spherical aberration should have no effect on visual resolution unless they exceed the depth of focus of an eye. Thus, our arguments imply that these factors may be relatively unimportant in small eyes with low acuity.
Article
Visual evoked potentials (VEPs) to temporal modulation of spatial patterns, recorded from humans ranging in age from 4-42 years, demonstrated that contrast-dependent responses exist in early childhood and change dramatically throughout childhood. Bright or dark isolated-check stimuli were used to emphasize contributions from ON or OFF pathways to the VEP. (ON and OFF pathways constitute one major pair of parallel subsystems, which process brightness [positive-contrast] and darkness [negative-contrast] information, respectively.) The developmental effects observed for each pathway were similar in magnitude and time course, suggesting maturation of a common physiological mechanism dependent on spatial contrast. Children's responses were more variable and larger than those of adults, and exhibited a relative phase lag. In addition, we recorded transient VEPs to a conventional contrast-reversing checkerboard pattern. The latency of the major positive wave (P100) was found to decrease, while the latency of the initial positive wave (P60) was found to increase, with increasing age. We propose a vector-summation model, which posits a relative decrease in cortical excitation with increasing age, to explain our major findings.
Article
To recommend a comfortable visual display terminal (VDT) workstation design in an aspect of visual ergonomics, physiological resting states of the eye in 3 visual systems, pupil, vergence, and accommodation, were objectively investigated in 3 experiments. Experiment 1 ascertained a positive display polarity (dark characters on a bright background) and an illumination level of 500 lx to be the most appropriate working conditions, by using pupil analysis and subjective visual comfort in 10 subjects. Dark vergence, in experiment 2, was evaluated to be at a distance of about 50 cm from the eye, as an average in 14 subjects. Dark vergence was found to shift farther with an upward gaze while a nearer shift occurred with a downward gaze. In experiment 3, the average dark focus for 11 subjects was found to be 1.4 diopters (D) or a distance of about 74 cm from the eye. The positive correlation between refractive status of the eye and dark focus was statistically significant (r = 0.602). The ergonomic recommendations for a VDT workstation obtained in this study are a positive display polarity with an appropriate lighting condition, a downward gaze, and a viewing distance between 50 and 70 cm. These recommendations are considered to reduce visual fatigue due to prolonged VDT work and to facilitate visual comfort at work.
Article
We have constructed a wave-front sensor to measure the irregular as well as the classical aberrations of the eye, providing a more complete description of the eye's aberrations than has previously been possible. We show that the wave-front sensor provides repeatable and accurate measurements of the eye's wave aberration. The modulation transfer function of the eye computed from the wave-front sensor is in fair, though not complete, agreement with that obtained under similar conditions on the same observers by use of the double-pass and the interferometric techniques. Irregular aberrations, i.e., those beyond defocus, astigmatism, coma, and spherical aberration, do not have a large effect on retinal image quality in normal eyes when the pupil is small (3 mm). However, they play a substantial role when the pupil is large (7.3-mm), reducing visual performance and the resolution of images of the living retina. Although the pattern of aberrations varies from subject to subject, aberrations, including irregular ones, are correlated in left and right eyes of the same subject, indicating that they are not random defects.
Article
In a series of experiments, proofreading performance was consistently better with positive polarity (dark text on light background) than with negative polarity displays (light text on dark background). This positive polarity advantage was independent of ambient lighting (darkness vs. typical office illumination) and of chromaticity (black and white vs. blue and yellow). A final experiment showed that colour contrast (red text on green background) could not compensate for a lack of luminance contrast. Physiological measures of effort and strain (breathing rate, heart rate, heart rate variability and skin conductance level) and self-reported mood, fatigue, arousal, eyestrain, headache, muscle strain and back pain did not vary as a function of any of the independent variables, suggesting that participants worked equally hard in all experimental conditions, so that the interpretation of the primary performance measure was unlikely to be contaminated by a performance-effort trade-off.
Light and Lighting – Lighting of Work Places – Part 1: Indoor Work Places (en 12464-1:2011)
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