f.lux

f.lux is a simple and easy to use application developed in order to provide you with the means of automatically adapting your desktop brightness and colors to the night / day lighting conditions.
This utility functions best when it knows your location details, as such it is recommended that you enter your geographical position, so f.lux can calculate the precise time of day and render the appropriate light tones. This is also advisable because the program has a hard time guessing your location.
After setting your position on the map, f.lux will determine your local time, placing your computer on a 24-hour transition schedule. You have the option of customizing the lighting for your screen for day and night time, ranging from 'Candle', to 'Halogen' and 'Daylight'.
In addition, f.lux enables you to preview an entire day's lighting changes in just a few seconds, so you can be certain your are happy with the settings, or go back and try again.
The application also offers a 'Movie Mode', that will attempt to keep the colors and shadow details, but still present images in warmer color tones, balancing powerful contrasts.
Moreover, you can turn off f.lux for an hour, if you need to work on something that is more color-sensitive and you want your computer to display images in their original tones, without any adjustments.
If you were ever blinded by an overly-bright computer when working at night or early in the morning, than you will immediately find use in f.lux. By adjusting your PC lights and colors to the time of day or night, you will spare your eyes from the effort of coping with high contrast levels between your room's lighting and your screen.
f.lux is a great tool that can help you feel more comfortable with your PC brightness and soften the shock your eyes face when switching from your computer to your ambient lights.