Andi Kleen's blog

A cool new desktop ergonomics tool I started using recently is redshift. redshift is a clone of the f.lux package, which also has Mac and Windows versions (There’s also another fork of redshift called redshift-gui, but I’m using the plain redshift which works fine for me)

Side note: some corporate firewalls seem to block the f.lux page because it contains flux minus dots (like the botnet?)

The basic idea is to adjust the light temperature of your screen to your inner clock and vice versa. Your inner clock running in a circadian rhythm regulates your sleeping schedule, body temperature and lots of other things. The human clock (or rather the clock of near all animals) does not have an exact 24hour period, but runs slightly slower. To keep your rhythm aligned to the day it regularly needs to be re-adjusted by a zeitgeber. This is normally done using day light input to your eyes, using brightness and light temperature (red for evening etc.)

Now the problem with people like me (and likely you) who do stare for long times into computer screens is that the lightening does not change there, unlike natural light. The light temperature stays cold like at noon, even if it’s in the middle of the night. This doesn’t give any cues to your internal zeitgeber.

You configure f.lux/redshift with your position and they compute the current position of the sun and adjust the light temperature of the screen based on that. This generally means that the screen gets more and more red towards the evening. In the night it stays still red

(I guess that’s not fully natural because real night is dark, but then a dark screen wouldn’t be very practical. Perhaps we had a few hundred thousand years to adjust to staring into red fire at night though, but I don’t want to get into evolutionary psychology style just so stories here)

This should make you more sleepy towards the evening and keep your sleep rhythm nearer normal day/night.

Does it actually work? I’m not sure, but I like it at least. (but perhaps that’s just because I don’t mind my screen having a red taint — you can tell what times of the day I prefer for work) Informally at least my sleep rhythm didn’t get worse from using it, and may be slightly better. I also like the visual indication of the time.

I guess I should do a comparison study and keep some data on the sleep rhythm while using redshift and not using it, but so far I haven’t had the energy to really set up such a experiment.

The f.lux page has some more theory and references.

One problem right now is that the X server gamma adjustment does not cover the mouse, so the mouse pointer in cold colors looks a bit out of place towards the evening. I wonder how hard it would be to fix that?

I also sometimes have to turn it off when viewing pictures or movies, but only rarely.

And when you travel you don’t have to forget to adjust the coordinates.

Interesting side question: how to set up the tool when you use the laptop during an intercontinential flight? Could it help with jetlag when used the right way? But how?