F.lux is a free utility that is useful if you use the same computer during the day and in the evening. F.lux will adjust the display on the monitor to match the lighting to the time of day. It’s easier on your eyes and might even help you sleep.
The program does not change the monitor brightness. Instead, it adjusts the color temperature – the amount of blue or red in the display.
Although it sounds odd, sunlight is fairly blue – “cool,” in the language of color temperature. Your monitor is even more blue. During the day that’s fine; it makes the display look bright and crisp.
At night, though, artificial lighting is warmer, with more red in it. At sunset F.lux adjusts the monitor display to make it warmer as well.
It’s a little jarring at first, especially if you’re watching at the moment that the settings change. For the first thirty seconds the display seems wrong somehow. I realized quickly though that the colors are adjusted but not wrong, and the warmer display is easier on the eyes in the evening. Now I install it on all my computers. It is available for Windows & Mac computers.
Setup is simple: provide your location so F.lux can determine when the sun rises and sets, then choose what kind of interior lighting you have. F.lux takes it from there, automatically adjusting the screen at sunset and sunrise in either a quick 20 second mode or gradually at an hour’s pace.
It’s restful on the eyes for work in the evening and there have been some studies suggesting that very blue light from computer equipment can actually interfere with sleep. Here’s a New York Times article about research into the effect of blue light on melatonin production.
It’s free and easy to install and uninstall. If you use the same computer day and night, give it a try!