The human body is designed to go through a repeating cycle of sleep and wake every 24 hours. The sun helps us to do that by changing the temperature of the light we see and experience. During the day, the light is bright and includes a lot of blue, which helps to keep us awake. In the early morning and evening, as the sun is rising and setting, there is much less blue. This helps us to wake up, and prepare to sleep, at the proper rate.
Computer screens also emit quite a bit of blue, just like daylight. Unlike the sun, however, computer screens don't adjust to help the body prepare for, or return from, sleep. Studies have shown that using your computer for an extended period of time at night before going to bed makes it much more difficult for you to get to sleep because your mind has been tricked into thinking that it's still daylight at 10:00p. Once you do finally get to sleep, your sleep quality is diminished for obvious reasons... one minute, your mind was told it was 2:00p in the afternoon, and the next, it's 11:00p at night. Talk about confusing! Well, there's an app for that. No, seriously!
Above is a graph that shows the amount of blue that is emitted from a typical computer screen. This helps to make images look really good to our eyes.
Below is a graph that shows the amount of blue (significantly reduced) that is emitted from a typical computer screen using an app called F.lux. This app is super-simple to use and is absolutely free.
F.lux will automatically just your screen to adapt and adjust to the time of day. As it gets later in the day, the amount of blue emitted is slowly reduced, just like a setting sun. Likewise, in the morning, it slowly returns to a normal state.
The result? You can supposedly go to sleep faster after using your computer and sleep better once you are asleep. Does it work? It's difficult to quantify, but I have been using it for a week now, and I can tell a difference.
You can download F.lux here for free! F.lux works on Mac, Windows, Linux and iOS.
One thing to be aware of... as the amount of blue is reduced from your screen, the image itself will appear more orange/red (again, like a sun setting). This will obviously throw images off, so you want to avoid doing image editing in the evening, for obvious reasons. If you do need to temporarily suspend the F.lux effect, you can choose to suspend it for short periods of time (up to "the next morning"), with will return the screen to a normal look.