What Level Of Screen Brightness Is Best To Protect Eyes?

Whilst the advancement of technology has undoubtedly brought us more good than bad, it’s widely accepted our physical and mental wellbeing will begin to suffer should our consumption of digital content be left unchecked. 

Again and again it has been shown that our health correlates with time spent staring at screens. And not in a positive way.

  • Higher rates of depression and loneliness are experienced by teenagers the more they invest time interacting with smartphones.
  • Using a computer for 5hrs per day can increase your frequency of feeling neck-shoulder and lower back pain.
  • More than half of us feel our eyes are left strained after spending too much time looking at screens.

One of the primary contributors to negative effects is over exposure to blue light generated by a bright display. 

Photo by Kelvin Design UK on Unsplash

Of all visible light, blue light has the shortest wavelength and so carries the greatest energy levels and exposure to very high intensity blue light can even cause damage to photoreceptive retinal cells in your eye, over time making them become less responsive. 

To be clear, blue light emitted by devices such as laptops and mobile phone screens is not high intensity, and so does not represent a biohazard even after long term viewing. 

Rather, overexposure to a bright screen causes us to experience something termed digital eye strain (DES) which manifests itself as headaches, blurred vision and reddened strained eyes.

So does screen brightness affect your eyes? Absolutely. And manufacturers know this too. 

Many of the leading technology firms have invested heavily in research and development budgets to create products that minimise the negative effects of digital displays. 

As an example, if you’ve ever read a book on a Kindle you’ll know that the display, including brightness and reflectiveness, is intended to look as similar as possible to a physical book. This deliberate design feature is not simply to enhance nostalgia but also to limit the negative effects that e-Readers have been demonstrated to have upon their users. 

So what is the best screen brightness?

Well unfortunately it’s a little difficult to pin point a precise brightness setting or value to use reliably across all devices in all settings. 

Firstly, if you were to quantify brightness levels the output would be measured in lumen (lm), lux or candela which straight way wouldn’t be the easiest of units to apply to your own displays.

Likewise opting for a standard brightness setting would equally be unhelpful as digital displays tell us how bright they are using an arbitrary scale. A 50% brightness setting on a Dell monitor for example will have a lumen output very different to a 50% brightness setting on a BenQ monitor. 

The best screen brightness to protect your eyes is one that is adjusted in response to ambient light.

The brightness should be set to allow text to be read without squinting or straining, but not be excessive to a point that causes your face to be basked in artificial light. 

The easiest way to find this sweet spot is to hold a sheet of paper next to your screen and adjust the display to mimic the brightness of the paper.  In a sunny well lit room this means the paper will be brighter, and so will the screen.

Is low or high screen brightness better for eyes?

Dim light causes eye strain, so although setting a low screen brightness might seem like it makes sense because it reduces the harsh effects of blue light, on the balance of things it could do more harm than good. 

As we’ve established the ideal brightness of a screen is variable and depends on the ambient light of the room you are working in.

This means that both a low and high screen brightness when taken to the extreme can be equally as harmful to your eyes.

If you’re forced to work in front of a bright screen (perhaps you don’t have control over the settings) or are exposed to the screen of a co-worker who enjoys staring at the sun there are a few things you can do:

  • Eye exercises: If you ask your eyes to work hard for long periods the muscles can effectively get tired and go into spasm. To give them a rest move away from your screen and focus on an object in the distance, at least 20ft away from where you stand. Do this for 20 seconds every 20 minutes. 
  • Blue light filter: Adding a filter such as the FORTIO screen protector is a cheap and easy way to control exposure to blue light and screen glare. Alternatively simply configuring the Night light setting in Windows (System Settings > Display > Brightness and Color > Night Light Settings) to control the output of blue light at certain times of the day. 

The video below from Doctor Eye Health provides tips and eye exercises for how you can prevent eye strain. It’s nearly 9 minutes long but a single watch will set you up with good habits that you’ll wish you had adopted into your routine long before today!

Is the auto-brightness setting on screens any good?

If you’re engrossed in your work or studies you could be forgiven for losing track of changing light conditions as the day passes. Unaware of the sun shifting from the cool natural light of the morning to the warm soft light of early evening.  

Rather than  manually changing the brightness of your screen to reflect constantly changing ambient light conditions it is possible to activate an auto-brightness function on many devices.

Ambient light sensors in your phone, computer or tablet detect the intensity of light shining upon it and this information is used to automatically adjust the brightness of your screen. 

The theory behind adaptive brightness is sound however initial applications came with a number of drawbacks including poor reactiveness and accuracy.

Since then advanced tech developments seem to have smoothed out the delivery of auto brightness with Apple’s TrueTone viewing mode being a good example of how things have changed. It allows iOS devices to accurately sense both white point and color to adjust both brightness and color temperature to match ambient conditions.

Some but not all PCs allow Windows to automatically adjust screen brightness. If you cannot find an adaptive brightness option in your settings (System Settings > Display) then a third party app such as f.lux , can be  used as a substitute. 

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