最近,由于黑暗模式的引入in IOS 13,记者让我评论了黑暗模式的可用性and its popularity as a design trend. It’s a question that I also got several times from attendees to ourUX会议

iOS 13:光模式(左)与暗模式(右)

I must say upfront that NN/g has not done its own research on dark mode. However, these questions prompted me to do a review of the academic literature on whether dark mode has any benefits for users — with normal vision or not. I will share these findings with you.

But first, let’s make sure we’re all on the same page by defining some vocabulary.

定义:对比极性是用于描述文本与背景之间的对比的术语:

  • Positive contrast polarity (light mode)指浅色背景上的深色字体文本。

  • Negative contrast polarity (dark mode)denotes the combination of light (e.g., white) text on dark (e.g., black) background.

暗模式显示器比光模式较少发光(而且,因为它,它们可能会延长电池寿命)。但环境中的光量不仅影响了功耗,而且是我们的看法。为了了解如何,让我们简要审查关于眼睛瞳孔的一些基本信息以及它如何对环境中的光量作出反应。

人类学生对光量敏感

The human pupil is the gateway to the retina: through it, light reaches the eye. By default, the human pupil changes size depending on the amount of light in the environment: when there is a lot of light, it contracts and becomes narrower, and when it’s dark, it dilates to allow more light to get in. Smaller pupil sizes make the eyes less susceptible tospherical aberrations出现无重点的图像()和increase the depth of field, so people don’t have to work so hard to focus on the text, which, in turn, means that their eyes are less likely to get tired. (Camera apertures work exactly in the same way: a photo taken at f/2.8 will have a narrower depth of field and thus more blurring than one taken at f/16.)

随着我们的增长,瞳孔大小减少。太小的瞳孔尺寸意味着太少的光进入了眼睛,这损害了我们读取或检测文本的能力,特别是在低环境光(例如,晚上)。在另一边,随着年龄的增长,我们变得更容易眩光,眩光在明亮的光线下特别可能。

Normal-Vision Users

在20世纪80年代进行的早期研究似乎指出,对于具有正常视觉或矫正至正常视觉的人(即,穿着适当规定的眼镜或接触),对比极性不会影响视觉性能。

Yet, several more recent studies contradict that initial finding. In particular, we will focus on two articles that involved two different types of tasks: one, published in 2013 in the journalErgonomics,looked at visual acuity and reading performance, and the other one, published in 2017 in适用的人体工程学,调查表演glanceable-readingtask — the quick reading of 1–2 words that people often engage in when they interact with a mobile phone, asmartwatch或者是汽车仪表板,并参与选中方向或参加通知等活动。

Effects of Contrast Polarity on Visual Acuity and Proofreading

Cosima Piepenbrock and her colleagues at the Institut für Experimentelle Psychologie in Düsseldorf, Germany studied two groups of adults with normal (or corrected-to-normal) vision: young adults (18 to 33 years old) and older adults (60 to 85 years old). None of the participants suffered from any eye diseases (e.g., cataract).

参与者有两种不同类型的任务:

  • 一种视力敏锐的任务,涉及检测A中的差距Landolt C optotype- 换句话说,向他们展示类似于以各种方式定向的字母“C”的符号,并要求它们识别间隙所在的位置(例如,顶部,底部)。
  • A proofreading task, which involved reading a short passage and identifying different types of errors

任务以不同的对比极性呈现 - 对于一些参与者,它们处于暗模式,对于其他参与者,它们以光模式显示出来。对比极性是一个between-subjectsvariable, meaning that each participant saw only tasks in one contrast polarity (e.g., only dark mode).

The researchers also collected pre- and post-test fatigue-related measures: participants rated their eyestrain, headache, muscle strain, back pain, and subjective well-being at the beginning of the experiment, as well as at the end.

Their results showed that light mode won across all dimensions: irrespective of age, the positive contrast polarity was better for both visual-acuity tasks and for proofreading tasks. However, the difference between light mode and dark mode in the visual-acuity task was smaller for older adults than for younger adults — meaning that,尽管老年人的光模式也更好,但它们并没有从中受益于年轻人,至少在视力任务中。

当研究人员看着疲劳度量时,他们得出结论,它们对其中的任何一个都没有显着差异(这意味着黑暗模式使人们更疲倦的情况,反之亦然)。

另一项研究,在期刊上发表人为因素通过同一研究组,研究文本大小如何在校对任务中以对比度极性交互。发现正极性优势随着字体大小降低而导致线性增加:namely, the smaller the font, the better it is for users to see the text in light mode.Interestingly, even though their performance was better in the light mode,participants in the study did not report any difference in their perception of text readability(e.g., their ability to focus on text) in light versus dark mode — which only reinforces第一规则可用性:不要听用户

Effects on Contrast Polarity on Glanceable Reading

Jonathan Dobres and his colleagues at MIT’s Agelab attempted to quantify whether ambient lighting conditions (simulated daytime compared to simulated nighttime) affect in any way the advantage of positive polarity in the context of a lexical-decision task. A lexical-decision task, a paradigm commonly used in psychology, involves showing participants a string of letters and having them decide whether it’s a word or a nonword. A lexical-decision task is more similar with the glanceable reading that we do in highly interruptible conditions such as when driving or using a mobile phone or smartwatch on the go — all of these involve quickly looking at a display and extracting the relevant information.

Agelab研究中的参与者具有正常或矫正至正常的视觉。它们以不同的环境灯(日间与夜间)和不同的字体大小,以两个可能的对比极性(暗模式与光模式)示出了字符串。

The study found that lighting, polarity, and text size all had an effect on performance — in the direction perhaps expected by now: simulated daytime lead to faster judgements than simulated nighttime, light mode was better than dark mode, and bigger font was faster than smaller font. The interesting result was the significant interaction between ambient lighting and contrast polarity:during daytime, there was no significant effect of contrast polarity, but during nighttime, light mode led to better performance than dark mode.此外,在夜间期间,人们在暗模式中阅读小字体文本比光模式更难。


人们在白天期间比夜间时间更快,在光线模式下比在暗模式中,较大的字体大小(4mm),而不是较小的字体尺寸(3mm)。在夜间期间,光模式明显优于暗模式,在光模式下,小字体更容易阅读。(较短的酒吧比较高的酒吧更好。请注意,实验中报告的时间措施是演示时间阈值;虽然从技术上比判断时间更复杂,但它基本上代表参与者对其进行正确评估所需的时间呈现字符串。)

模拟日间环境中极性缺乏效果有些令人惊讶和与Buchner和Baumgartner不同的旧研究,也看过明亮的VS暗环境条件。然而,在该研究中,明亮的环境光远低于Agelab研究中使用的环境光(思想办公室光与明亮的户外灯)。Dobres和他的同事们认为环境光量可能会影响正极性优势,明亮光线导致零差,但正常的办公灯仍然能够产生差异。

Long-Term Effects

到目前为止审查的文献介绍了对比极性对人类性能的一次性影响。但长期效果怎么样?换句话说,长期暴露于一种类型的对比度极性有任何效果?

2018年在自然研究的科学报告中发表的一个有趣的研究表明,持续暴露在光明模式可能与近视有关。近视(或近视)是指无法清楚地看到远的物体,并与教育水平和阅读强烈相关。在他们的学习中,德国蒂宾根大学的Andrea Aleman和她的同事要求7人参与者在暗模式和光线模式下读出一小时的读取文本。为了看看近视后对近视的倾向改变,它们测量了脉络膜的厚度,视网膜后面的血管膜。脉络膜的细化与近视有关。

The researchers found significant thinning of this membrane when participants read text presented in light mode and significant thickening when reading text presented in dark mode. The thinning was more pronounced in participants who already had myopia.

This result seems to suggest that, even though performance in light mode may be better in the short term, there may be a long-term cost associated with it.

Users with Impaired Vision

对愿景受损的用户的文献是矛盾的,比具有正常愿景的人的族人,尽管存在隐含的共识,但黑暗模式至少对于一些具有视觉损伤的人来说,黑暗模式更好。明尼苏达大学的戈登克莱格及其同事定义了两种低视图类别:(1)由于中央视觉障碍和(2)由于阴天眼镜媒体。

眼介质是指眼睛中的各种透明物质,包括角膜和镜片。阴天眼镜媒体最常见的原因是cataract, which refers to the clouding of the lens and is fairly common in older people. A cataract scatters and blocks some of the light that is supposed to reach the retina through the lens and thus prevents the creation of a clear, focused image on your retina.

Even as early as 1977, a study by Sloan reported that some people with low vision prefer dark mode. (In我们自己的无障碍研究,卡拉Pernice还看到了低视野的用户有时会在黑暗和光线模式之间切换,以试图获得清晰度。)1985年,明尼苏达大学的Gordon Legge和他的同事假设这一效果是由于“异常光线散射到期ocular media” — presumably, because, if more light reaches the eye with a cloudy lens, there’s a bigger chance of a distortion. Thus, dark mode may be better for people with cloudy ocular media because the display emits less light.

在亨格的研究中,7中的每一个participants with cloudy ocular media had better reading rates with dark modes, whereas the rest of the participants, who had impaired central vision, were not affected by contrast polarity.

克格格的研究成了推荐切换到现代计算机接口的黑暗模式的可能性的基础。2005年,Papadopoulos和Goudiras在一篇文章中审查了低视用户的各种可访问性最佳实践的文章中,建议在用户界面中的暗模式的可用性。

正常视觉领域的几个研究人员指出的警告是,用CRT显示器进行钢琴的研究,与大多数现代显示器中使用的LED相反。这些显示器更容易在光模式下闪烁而不是在暗模式中,因此可能偏置对光模式的结果。

Takeaways

那么,你应该跳上黑暗模式的潮流吗?虽然黑暗模式可能对某些低视网膜用户提供一些优点 - 特别是那些具有多云眼介质如白内障的那些,研究证据是正常视觉用户的正极性的优势方向的方向。换一种说法,在具有正常视觉的用户中,光线模式大部分时间都会导致更好的性能。

Why is light mode better for performance? These findings are best explained by the fact that, with positive contrast polarity, there is more overall light and so the pupil contracts more. As a result, there are fewer spherical aberrations, greater depth of field, and overall better ability to focus on details without tiring the eyes.

Even though larger font sizes and bright ambient light may erase some of this advantage in people with normal vision, at this point we don’t recommend switching to dark mode by default if your target audience includes the general population.

That being said, we strongly recommend thatdesigners allow users to switch to dark mode if they want to— for three reasons: (1) there may be long-term effects associated with light mode; (2) some people with visual impairments will do better with dark mode; and (3) some users simply like dark mode better. (We know that people很少更改默认值, but they should be able to.) It’s unlikely that people will alter the display mode for any random website, but, if a website or an application sees frequent use, it should consider providing this option to its users. In particular,应用程序意味着长形阅读(如书读读卡器,杂志,甚至新闻网站)应提供暗模式功能。该选项应该理想地在该网站或应用程序的所有屏幕中普遍存在。此外,如果操作系统提供黑暗模式API(如iOS),请确保您利用它 - 这样做将为那些决定切换到黑暗模式的用户能够在其所选中介绍您的应用程序或网站对比极性。

参考

A. Aleman,M. Wang和F. Schaeffel(2018年)。阅读和近视:对比度极度。Scientific Reports8,10840(2018)DOI:10.1038 / s41598-018-28904-x

J. Dobres, N. Chahine, B. Reimer (2017). Effects of ambient illumination, contrast polarity, and letter size on text legibility under glance-like reading,适用的人体工程学DOI:10.1016 / J.Akergo.2016.11.001

G.E.LACGE,G. S. Rubin,D.G.Pelli和M. M. Schleske(1985)。读书的心理物理学 - II。低视力。Vision Research

K.S. Papadopoulos., D. B. Goudiras (2005). Accessibility Assistance for Visually-Impaired People in Digital Texts.British Journal of Visual Impairment.DOI:10.1177 / 0264619605054779

C. Piepenbrock,S. Mayr,I. Mund&A. Buchner(2013)。阳性显示极性对于年轻人和老年人来说是有利的,Ergonomics, DOI:10.1080/00140139.2013.790485

Cosima Piepenbrock, S. Mayr, A. Buchner (2013). Positive Display Polarity Is Particularly Advantageous for Small Character Sizes: Implications for Display Design.人为因素。DOI: 10.1177/0018720813515509

L.L. Sloan (1977). Reading Aids for the Partially Sighted: A Systematic Classification and Procedure for Prescribing. Baltimore, MD: Williams & Wilkins.