If you're reading this late in the day, pause to consider your eyes. Can you feel that familiar sting that comes from looking at a glaring LCD for too many hours? That's only the most noticeable symptom of what happens to our bodies when we spend hours staring into what's essentially a big, bright, lamp. F.lux is a simple and free app that helps fix this.

f.lux knows what time the sun sets wherever you are.

Turning down your monitor's brightness may help, but brightness isn't really the main issue: Color temperature is, and that can be trickier to adjust. Most computer screens emit bluish light that looks good in daytime, but becomes uncomfortable to look at in a dark room. It can also affect your sleep: Research suggests that reading on a tablet for two hours before bedtime can delay your sleep by about an hour.

F.lux helps by asking you where you're located in the world, then figuring out the approximate sunset time for your location. Come sunset, your screen will mimic nature, gradually warming up the colors and blending in much better with the surrounding light. You basically get your own private mini-sunset, ending up with a screen that's nice to look at.

f.lux now lets you adjust your monitor's brightness with keyboard shortcuts.

This basic functionality—tuning your screen's color temperature according to time of day—has been part of f.lux for years now. A recent version adds some new bells and whistles: You can now change your screen's brightness using Alt+PgUp and Alt+PgDn. This isn't exciting if you use a laptop, but for a desktop user like me, it's a great feature.

Another new feature is the so-called Darkroom Mode. Whereas the normal f.lux effect just warms up your colors, Darkroom Mode completely takes over your display, shading everything in dark, reddish hues. This makes videos unwatchable, but also means you can probably use your computer at 3am without losing your night vision.

You can dial in your own nighttime color temperature to suit your environment.

Since we don't all work with the same ambient lighting, f.lux lets you dial in a color temperature for nighttime. It uses Kelvin notations (commonly used for color temperatures), but also offers human-readable explanations ranging from "Ember" (1200k) to "Sunlight" (5000k).

All of these color changes are great, unless you happen to be trying to watch a movie. That's where Movie Mode comes in: This mode tones down the color effects for 2.5 hours, to let you watch a movie without having everything tinged red. You can also completely disable f.lux for one hour (for doing color-sensitive work such as photo editing), or until the next morning.

F.lux was a very good app to begin with, and this release only makes it better. If you're not using it yet, but do use your computer at night, you really should try it out today.

Note: The Download button takes you to the vendor's site, where you can download the latest version of the software.

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