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Night Shift: How blue light impacts sleep, and what companies like Apple can do about it

When Apple launched iOS 9.3 last month, it included support for a new feature known as Night Shift. Night Shift is designed to reduce the amount of blue light emitted by an iDevice’s display to reduce the sleep disturbance often created by late-night browsing sessions on a smartphone or tablet. DisplayMate recently put Night Shift through its paces to determine how well the technology works, and wrote an extensive article on both current best practices and future design recommendations.

First, a bit of background. Over the past few years, a growing body of research has found a significant, repeatable effect on the body’s production of melatonin and the spectrum of light would-be sleepers are exposed to immediately before going to bed. Lower melatonin levels are linked to both difficulty falling asleep and less restful sleep in general, and the long-term health consequences of insufficient rest can be significant. One reason for this problem is that the display spectra of modern LCDs is distinctly different from the sun.

Sunlight vs. white LED

Current data suggests that blue light in the 460-490nm wavelength is what’s most disruptive to human sleep patterns. As the image above shows, white LEDs have a very strong blue component smack-dab in a sleep-disrupting wavelength, whereas full noon sunlight has an altogether different curve. While the sun is thousands of times brighter than any LCD (just try using one outside if you don’t believe us), smartphones and tablets are used just inches from our eyes — much closer than any monitor or television.

Apple’s Night Shift is a new option for 64-bit smartphones running iOS 9.3, but it’s not a fundamentally new capability; programs like f.lux have been available for years on Android, Windows, and Linux (f.lux can be installed to jailbroken iOS devices, but has never been available from the App Store). Night Shift is designed to reduce the total amount of blue light emitted by the display. According to Dr. Soneira, the middle Night Shift option cuts blue light emissions to 57% of normal, while the far-right option takes blue light down to 42% of its baseline.

With Night Shift set to maximum, the screen’s red output is also boosted, further shifting the final image to a distinct orange output. The image below, from AppleInsider, neatly captures all three states.

Night Shift

Obviously the last option isn’t very attractive for… well, anything, honestly, but if you suffer from sleep disruptions a good night’s rest can be worth far more than a temporarily off-kilter LCD. It’s not yet clear if display spectra adjustments like these are enough to offset the impact of the increased blue light from LCDs; more research will need to be done with devices that use f.lux or Night Shift to measure the impacts.

The full DisplayMate piece goes into additional detail, including how quantum dot LEDs could be used to create displays that emit less blue light without tinting them a distinct shade of yellow/orange. For apps that support it (such as Kindle), choosing white text on a black background and dimming the display as much as possible works well, at least for reading books. Until new display technologies come of age, adjusting existing display light levels is the best we can do — unless you want to pay big bucks for a pair of glasses with an expensive, blue-specific notch filter, anyway.

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