Debunked: Night Light/Shift Is Actually Worse for Your Sleep

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Vivo V17 Pro Yellow Tint
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People are always going to be on their phones and that’s why there’s night shift on iOS devices and some form of Night Light on Android phones that come with different naming with toggles for Eye Care, Eye Comfort or a Blue Light toggle for Samsung Phones. Enabling this feature on your phone gives the display a kind of yellow tint that reportedly helps users reduce the time they spend on their phones especially in the evening as they get ready to sleep.

Blue Light Filter on the Samsung A20
Blue Light Filter on the Samsung A20

There’s a plausible scientific principle on why a yellow tint was chosen. Melanopsin, a protein in the eye responds to light intensity and will respond more strongly to the light of a shorter wavelength. Light wavelengths correspond to how we perceive its colour. Our phone’s displays have three “subpixels” lighting each pixel of the display, in the colours red, green and blue.

Vivo V17 Pro Eye Protection
Vivo V17 Pro Eye Protection

The blue pixel is the shortest wavelength and so the night light/night shift(Eye Care, Eye Comfort, Eye Protection) either reduces the blue subpixel’s brightness or turns it off immediately giving the screen that yellow tint.



Well, the University of Manchester released a study that says the yellow tint is even worse for helping you get to sleep than just using the phone on its default untinted setting.

The study points out the marginal benefit provided by making the average wavelength of the light emitted by your phone’s display longer (i.e., warmer) is probably outweighed by another factor related to the ways your eyes affect your biological clock.

“Twilight is both dimmer and bluer than daylight, they say, and the body clock uses both of those features to determine the appropriate times to be asleep and awake. Current technologies designed to limit our evening exposure to blue light, for example by changing the screen colour on mobile devices, may, therefore, send us mixed messages as the small changes in brightness they produce are accompanied by colours that more resemble day,” the UOM team argues.

The UoM team carried out this research on mice using specially designed lighting that allowed the team to adjust colour without changing brightness proving that blue colours produced weaker effects on the mouse body clock than equally bright yellow colours.

These findings have important implications for the design of lighting and visual displays intended to ensure healthy patterns of sleep and alertness.

“We show the common view that blue light has the strongest effect on the clock is misguided; in fact, the blue colours that are associated with twilight have a weaker effect than white or yellow light of equivalent brightness. There is lots of interest in altering the impact of light on the clock by adjusting the brightness signals detected by melanopsin but current approaches usually do this by changing the ratio of short and long wavelength light; this provides a small difference in brightness at the expense of perceptible changes in colour,” said Dr Tim Brown, from The University of Manchester.

“We argue that this is not the best approach, since the changes in colour may oppose any benefits obtained from reducing the brightness signals detected by melanopsin. Our findings suggest that using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial. Research has already provided evidence that aligning our body clocks with our social and work schedules can be good for our health. Using colour appropriately could be a way to help us better achieve that,” he continues.

If you want to get to sleep quickly, just put the phone down.

Here are handy tips to help you use your phone less.

It is not the colour of the screen that is keeping you awake; it is all the stuff your phone offers as an alternative to sleep at 2am.

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