Free app adjusts color on monitors to prevent disruption of sleep cycle By Greg Linch Washington Post Staff Writer Monday, February 14, 2011; 3:29 PM I stare at screens almost every waking hour. Computer monitor. Laptop. Tablet. Smartphone. So I've tested a few ways to ease the strain on my eyes - and, in the process, learned about something that might be helping me in non-waking hours, too. It's about the light that these screens emit. It typically has a cool blue undertone, whether you notice it or not. Think of your next-door neighbor's TV seen through a window at night. That's fine during the day - screen light was designed to mimic the tones of daylight. But my screen time lasts long after dark. And that's the problem. Humans evolved to respond to darkness by producing melatonin, the hormone that regulates the sleep cycle. But our light-sensitive pineal gland near the center of the brain responds to blue light by suppressing melatonin, causing us to wake up. When we see too much blue light in the late evening, it delays or disrupts the melatonin rush. In other words, my iPad can keep me up even after I turn it off. But just as technology can cause this problem, it offers a solution as well. Enter F.lux, a desktop application that adjusts a computer screen's color throughout the day. During daylight hours, the screen's undertone is the familiar blue. As sundown approaches, it begins transitioning to a warm shade of red-orange. In the morning, it's cool blue again. If I'm browsing the Web or reading text, the warmer backlight color doesn't bother me - it reminds me of the sepia setting I use for iBooks on my iPad. I also hardly even notice the difference sometimes when looking at photos or watching videos. Thankfully, if something does look a little too strange, F.lux allows me to disable it for an hour at a time for color-sensivitive activities. The software application, which launched in February 2009, is available to download for free on Windows, Mac and Linux. I've been running F.lux on my MacBook Pro since last summer, and I seem to be sleeping a little better. Or am I? Maybe I just think I'm sleeping better, getting some kind of electronic placebo effect. But does it matter? Do you use any apps or gadgets to track your sleep? If so, please share your experience.