In the not-so-distant future, your personal tech will behave like the sun. It will rise and shine brightly in the morning, and set and dim its lights as the day winds down. In a recent preview for iOS 9.3, Apple teased a new feature called Night Shift that does exactly this, automatically altering the color of your screen display to make it orange-colored in the evening. Last month, Amazon released a similar feature, called Blue Shade, in an OS update for its Fire reading tablets. The new feature lets nighttime users dim the amount of blue light that comes off the Fire’s screen, in favor of a mellow, amber glow.

Apple’s feature technically doesn’t exist yet, but the point of it, and Blue Shade, is simple: to let us get some sleep. The underlying tech—blue light that fades into orange light as the day wanes—is a direct response to a large and growing body of evidence that suggests late-night exposure to artificial light can disrupt your body's circadian rhythms, light-triggered physiological changes that regulate bodily functions ranging from sleep to metabolism.

Apple declined to talk to WIRED about Night Shift, saying that it’s still in development, but Aaron Bromberg, senior manager of product management for Amazon Devices, says the feature was created in response to customer feedback. “We’ve been keeping an eye on nighttime reading for more than a year,” he says. “Customers told us this was something that was on their mind—that they were worried about using their tablets or mobile devices to read in bed—so we started to dig deeper.”

But First, F.lux

This light-shifting technology, while novel to Apple and Amazon, isn’t new. As the 15 million people who’ve downloaded f.lux can tell you, software that turns your computer screen orange has been available for years—seven, to be exact. But it’s only now that this bit of UX seems poised to go mainstream.

F.lux was founded almost by accident. In 2008 Michael and Lorna Herf had recently left their jobs working on Google’s photo management tool Picasa, and were living in Santa Monica. Lorna is a painter and used the upstairs loft in their apartment for her studio, where she would often work through the night. She quickly ran into a problem: Even with lamps and lightbulbs, the lack of sunlight obfuscated the hues of her paints, messing up the outcome of her work. “All the colors came out completely wrong, and this thing she thought to be, say, orange would be bright pink,” Herf says of his wife’s dilemma.

With Michael's help, Lorna rigged the studio with bright light bulbs that simulated daylight by emitting an excess of blue wavelengths. It helped her paint with accuracy—and alertness—through the night. Then Lorna noticed something. “One night she came down from the brightly lit daylight room,” Herf says, “and she came downstairs to our living room, which is dim, and said: ‘All the computers have the wrong color. They look like the daylight room.’ So we made a tool to try and fix that.”

That tool was a rudimentary command line app where you would request a color filter, and get it immediately. It started as an experiment more than anything, and Herf says he and Lorna found that they felt more relaxed with the orange screen filters turned on at night. They started researching the topic in earnest, partly inspired by Lorna’s memory of a science class she once took. “She remembered from a biology class that birds migrate according to season, and a lot of it is about blue light,” Herf says. “So when we posted it to [my website] we said, hey, this might be connected.”

For ages, parents everywhere have warned their kids about the ills of sitting too close to the television screen; today, that concern has been recast into a worry that staring for hours on end at our laptops, tablets, and phones can't be all that good for our health. Science backs this up: Studies have shown that exposure to certain wavelengths of blue light can suppress melatonin production in humans. Melatonin is a hormone that helps induce sleep, and it “is a robust marker of circadian rhythmicity,” says Richard Stevens, a cancer epidemiologist at the University of Connecticut Health Center who has studied the physiological effects of light exposure for more than two decades. In other words: more screen time equals less sleep time.

Amazon

As our understanding of light exposure has evolved, so has the tech. Soon after rolling out the first iteration of f.lux, Herf wrote new code to make it respond automatically to the user’s local sunrise and sunset. These days, f.lux users can tailor it more specifically to their unique schedules. To develop Blue Shade, Bromberg says Amazon’s display technology designers were tasked with filtering out blue light wavelengths, without compromising legibility and battery life. “It’s very easy to implement a screen dimmer,” he says. “If you imagine a prism of light that covers all of the visible wavelengths, it’s very easy to just lower the intensity equally. The problem with that is that a lot of content, especially black text on a white background, will still have a peak intensity around the blue part of the spectrum.” Ultimately, Amazon’s team had to engineer the screen’s display light to both suppress blue light and increase light from other parts of the spectrum. The result is a peachy backdrop that’s reminiscent of the Financial Times’s salmon pink paper color. Details are scant on how Apple’s Night Shift will work, but the company’s preview page for the new iOS says, “it automatically shifts the colors in your display to the warmer end of the spectrum, making it easier on your eyes.”

More Than Just Screens

It's too early to tell whether these new features will translate to healthier or more well-rested users. Stevens says the way our retinas and our Circadian clocks perceive light is different, and deserves more research attention. Herf, while not a scientist, says that tech industry has been too quick “embracing [the research] as science,” and that “these one-size-fits all solutions are not the right idea,” and that seasons, individual schedules and genetics all come into play. (His frustration is understandable, given that Apple recently ordered f.lux to remove its app from the App Store, ostensibly to eliminate the incumbent competition before launching Night Shift.)

Both Herf’s skepticism and Stevens’s perspective suggest Night Shift and Blue Shade are just the beginning for dynamic lighting technology. Herf won’t say what’s next for f.lux, but says he and Lorna are focused on advancing the research that looks at people’s unique preferences and reactions to different kinds of light. (He’s also petitioning Apple to allow f.lux back on iOS.) It’s hard to say exactly what form this technology will take, but Stevens think it’s about more than just screens—it’s about all light. “This area—lighting technology, by time of day—is a very big and very deep deal,” he says. “It’s not a fad diet, it’s not going away.”