f.lux is a free piece of software that slowly shifts the color temperature of your computer monitor throughout the day in order to adapt it to the natural rhythm of light. I first downloaded it after reading about Seth Robert’s self-experimentation involving sleep. As Roberts points out, research indicates that certain color temperatures stimulate wakefulness and affect circadian rhythms. This is why people with Seasonal Affective Disorder use blue light devices that supposedly mimic the blue sky of summer. By using f.lux to shift the temperature of a computer monitor away from blue light and towards red after natural light has faded the idea is that it will diminish the unintended wakefulness caused by the screen and allow for a more restful sleep.
While I am not as careful a self-experimenter as Seth Roberts, I have noticed that when I use f.lux not only do I get sleepier sooner but that I also awake earlier. By simply disabling the program for an hour (an option that is built into the software) I also notice an immediate sense of renewed wakefulness. The shift in color temperature is significant and immediately noticeable when I use my computer at night, but not in a way that negatively impacts the quality of the image on screen (and when it does, or if I need to edit photos, I simply disable it).
The program is available for Mac OS X and Windows XP/Vista/7. A similar program called Redshift is available for Linux users.