Light temperature, Sleep, and F.lux

I posted again over at The Primal Challenge today. Here is the post, in its entirety, below:

I don’t know about you, but the “no glowing rectangles an hour before bed” rule is difficult for me. At Hillsdale I am usually so busy that I can’t avoid using my laptop before bed, lest work go unfinished. That used to affect my sleep a great deal, but then I came across a tip in Matt Madiero’s book, Roots.

Matt recommends a great piece of freeware called F.lux. Made by Stereopsis, F.lux is a free, cross-platform (Windows, Mac, and Linux) piece of software that changes the color temperature of the screen on your computer at night to the ambient light around you. Normally, screens are set around 6500 K, roughly the temperature of sunlight, which is great for waking you up, but not for allowing you to fall asleep. Some CRTs go all the way up to 9300 K. F.lux changes your screen temperature at sunset to around 3400 K, which is roughly the temperature of halogen light.

When I first installed the software, I didn’t think it made a noticeable difference until I turned it off a few hours later in order to edit some photos. When I turned F.lux off, the screen hurt my eyes! I can’t definitively say it has improved my ability to fall asleep since I’ve used it because I am getting more exercise during the day and I am usually exhausted by the time I go to bed, anyway. Since turning it off hurts my eyes so much, though, I suspect that f.lux is at least not hindering my brain from making melatonin to make me sleepy.

Stereopsis cites a lot of research which deals with the effects of color temperature. Here is an excerpt:

“…we surmise that the effect of color temperature is greater than that of illuminance in an ordinary residential bedroom or similar environment where a lowering of physiological activity is desirable, and we therefore find the use of low color temperature illumination more important than the reduction of illuminance. Subjective drowsiness results also indicate that reduction of illuminance without reduction of color temperature should be avoided.”
– from the paper: “Effect of Illuminance and Color Temperature on Lowering of Physiological Activity”

So, does this mean it is okay to use your computer all of the time before you go to bed? No. It is still best to keep things pretty low-key and dim before you go to bed. You should also avoid having lights in your room at night. (I covered up all of the lights on my gadgets.) When you must use your laptop at night though, lower the color temperature with F.lux. Also, if you are the type of person who reads for an hour before bed, use a bulb with a lower color temperature. Wikipedia has a good chart of common bulb color temperatures.

Want to know something interesting? Those most of those curly florescent bulbs that Congress is trying to get you to buy are around 5500 K. So not only do they contain mercury and are more expensive than incandescent bulbs, but they are also ruining your ability to fall asleep. As Bastiat noted so long ago, government intervention has unintended consequences.