For thousand of years our days have been scheduled by the sun, so it is no surprise that our biological clock can be directly affected by the amount of light we get. Yet, our bodies can not differentiate sun light from artificial light, and in our modern societies we are surrounded by the later until the very last minute we go to sleep.
Melatonin is the hormone that tells our body when it is time to sleep, but it secretion can be affected by exposure to bright light, specially blue light of which we get a lot during day time, while red light, like that for example of sunsets, does not hamper our sleep cycle. The effect of light on our daily cycles has been studied by Harvard among others.
In this post I am going to talk about software to automatically reduce the amount of blue in your screen without you even noticing it according to the time of day. Remember that screens produce any color by mixing red, green and blue light sources.
F.lux is a powerful tool that lets you easily configure and personalize automatic color shifts according to the day of time by using your coordinates or zip-code.
It is also possible to configure F.lux for smooth or abrupt color change, as well as the minimum and the maximum color temperatures you like. This is a great option for those people who want to reduce the amount of blue light with minimum impact of the displayed on-screen colors.
Fl.lux is available for Windows, Linux and Mac devices. However, I was very disappointed with the Linux port, which does work as intended, but comes with a terrible graphical user interface.
Redshift is free software under GPLv3 license inspired by F.lux. It is written mainly for Linux, but you can also find it for BSD and Windows. It was originally intended to be run and configured as a command line tool, although it is possible to use a graphical user interface as I am doing right now.
The behaviour is very similar to that of F.lux, with a tray icon (in the GUI version) that allows for status control and color shift suspension for 0.5, 1 and 2 hours. Configuration is not as intuitive as in F.lux, because it has to be done using a text configuration file, however, default configuration works so good I did not even need to change it.
The first think noting is that although you clearly see the difference of color in the above picture, in practice your eyes compensate for the reduced amount of blue and you absolutely do not notice the filter at all. This is the same effect that happens at night when you walk the streets under the orange light of High Pressure Vapour Lamps: your brain compensates and you are still able to see other colors. Also, the gradual change helps a lot, which during an hour gradually reduces the screen's temperature.
Regarding whether to use F.lux or Redshift, if you are using Windows or Mac go with F.lux, but if you are a Linux or BSD user, absolutely go with Redshift.
I have been using both softwares for about two years now, and since I started using them I have stopped laying in bed with a tired body but an anxious mind after staying late into the night working on the computer. 100% recommended.
P.S.: I have seen some fancy adhesive plastic filters for smart phones and tablets sold at ridiculously prices which do exactly the same thing these programs do. Please do not waste your money on those.