The "dark mode" you see in iOS 13 is actually not eye protection

The bright white background is gradually being replaced by deep black, which is described as a trendy and cool new UI design paradigm. In the upcoming iOS 13 and Android Q systems, Apple and Google have made "dark mode" one of the main updates this year.

Some people are used to calling it "dark mode", which sounds like it is tailor-made for darkness, even though this is indeed one of its usage scenarios.

But if you plan to use it to alleviate the damage to your eyes caused by playing with your phone before going to bed, you may have to give up the idea.

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In the Android developer documentation, Google has described three advantages of dark mode: improving battery life, improving visibility for people with low vision and those sensitive to strong light, and allowing users to better use the device in low-light environments.

The improvement in battery life is related to the screen material of the phone. Taking Google's test data as an example, it used an iPhone 7 with an LCD screen and a Pixel phone with an OLED screen for comparison. When the two used map navigation after enabling dark mode, the power consumption of the Pixel phone dropped by 63%, while the iPhone 7 did not change much.

However, the following two points related to eye use are not recognized by everyone. The key question is "whether dark mode can really improve our visibility and readability of text", or even whether it can achieve the effect that "using dark backgrounds can protect our eyes" as some people claim.

The answer is not clear at the moment.

As early as 2003, Taiwan's Dayeh University conducted an experiment to test the impact of dark and light backgrounds on user screen readability. The results showed that when dark text was on a light background, the subjects read faster and completed the task better; Susanne Mayr, a researcher at the University of Passau in Germany, also came to a similar conclusion.

At the same time, Euna Koo, a doctor from the Bayers Eye Institute at Stanford University, also said that based on the existing data, she does not think that dimming the screen tone can relieve eye fatigue. Compared with the tone, the user's usage time and screen brightness are more worthy of attention.

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In the past, we talked about the problem of screens hurting the eyes, which was essentially about factors such as blue light or stroboscopic light. The former refers to the short-wave visible light in the light source, which affects the macular area of ​​the human eye, thereby reducing sleep quality; while the latter can be understood as the frequency of fluctuations in the screen image, which may aggravate visual fatigue and exhaustion.

Because of this, you can now see various film accessories with the slogan of "anti-blue light" on the market. This year, several domestic mobile phones have begun to pay attention to the flicker problem of mobile phone screens and have provided corresponding solutions. Both have no direct relationship with the screen color.

A study from the Visual Perception Interaction Group at the University of British Columbia shows that if "astigmatism users" are asked to read white text on a black background, it will be more difficult than reading black text on a white background.

The reason is that, in the case of black text on a white background, the human eyes can receive more light, more parts of the iris will choose to close, and the deformation of the lens will be relatively small; but in the case of white text on a black background, in order to increase the absorption of light, the iris will open wider, the deformation of the lens will also become larger, and it will be more likely to cause eye fatigue.

"Especially when the font size is very small, such as when reading a text message on a small screen phone, a light background will clearly outperform a dark background."

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An Apple engineer also said that the discussion of the value of dark mode for mobile phone users cannot be separated from the influence of external conditions such as ambient light.

For example, when you look at your phone in low light or even in total darkness, it is inevitable that you will have the problem of being too glaring. At this time, the dark mode and the "True Tone Display" function are designed to adjust the phone screen to a color temperature close to the surrounding ambient light, thereby improving user readability.

This is just as Google said. Dark mode can indeed provide some help for users who are sensitive to strong light and in low-light environments, but it still has no direct connection with eye protection.

At last year's WWDC conference, Raymond Sepulveda, a designer from Apple's human-computer interaction team, further explained the usage scenarios of macOS' "dark mode".

He pointed out that only reading, browsing or content creation apps need to enable dark mode for a long time, such as text or code editing. They will use the high contrast characteristics of black background and white text to keep the user's eyes focused, while most other software do not have a strong demand for dark mode.

Interestingly, some content consumption apps have also taken a fancy to the feature of dark background - such as Spotify, Netflix and Steam, which all use dark background as the default design style. It is not so much for focusing attention, but rather trying to retain users, extend usage time, and make them indulge and addicted.

Therefore, hoping to improve our mobile phone usage habits with dark mode, screen time or other things is more psychological comfort than practical significance. If you really want to protect the health of your eyes, why not convince yourself to put down your phone before going to bed?