Each evening at sunset, f.lux warms up the colors on your phone. At dawn, f.lux returns your phone to daylight colors. We made f.lux because one day we noticed that all our laptops were the wrong color temperature at night. They looked fine during the day, but at night, they were much too blue. We realized that looking at the sun all night long might not be such a good idea. After researching blue light's effects on health, we found lots of evidence that color matters even more than brightness. And it turns out that timing matters, too: Blue light during the day is great for your circadian rhythm. Blue light at night is not.
February 12, 2017