Charly's Column – f.lux

If you ask me, it has to be possible to adjust lighting to suit your needs in an unobtrusive and fully automated way. I enabled night mode on my Android smartphone. In the evening, the display shows an ever-decreasing amount of blue light as time progresses. At first, this seems a bit strange and takes getting used to, but it is very friendly on the eyes. Without night mode, I get dazzled when I unlock the phone. This is because its display – like most monitors – is adjusted to a color temperature of 6500 Kelvin.

Cirque du Soleil

Light with a temperature of 6500 Kelvin has a higher blue component than sunlight, which does not exceed 5800 Kelvin even on a clear day. For work during the day in a bright room, 6500 Kelvin is completely OK. In the evening with dim light, I feel as if my PC displays are so bright that work becomes tiring. Of course, I could manually adjust the brightness and color temperature using the buttons on my displays – but that is something that I want to be done automatically. My choice of dimmer goes by the name of f.lux.

Installing f.lux

F.lux is simply pronounced "flux". It is available as a command-line tool [1] or with a GUI [2]. I decided to go for the graphical variant. F.lux is written in Python 3, which means quickly installing some packages on my Ubuntu test system for it to run:

sudo apt install python3-distutils gir1.2-appindicator3-0.1 gir1.2-gtk-3.0

Guidance for other distributions can be found at the same source. Then I added the repository and installed the fluxgui package:

sudo add-apt-repository ppa:nathan-renniewaldock/flux
sudo apt update
sudo apt install fluxgui

At startup time, I had to tell f.lux my approximate geographic position (Figure  1). In return, it actually showed me a map, guessing my location based on my IP address. (It was about 100 kilometers away, but that was totally irrelevant from a lighting point of view.)

Figure 1: You'll enter the latitude and longitude of your location, as well as the color temperature value the display should switch to at night.

Then I specified the maximum color temperature to which f.lux can reduce the display at night. I initially chose 3500 Kelvin, which seemed to be warm enough in preview mode.

After a few evenings using the computer, I will know whether I need to readjust this value. In any case, there are enough options for this (Figure 2). Finally, to be on the safe side, I checked again whether the time zone and time are set correctly; I don't want f.lux to intervene at the wrong time of day.

Figure 2: Kelvin home alone – light sources and their color temperatures.

F.lux is also available for Windows and macOS. Enlightenments thus far: Everything is now to my liking in terms of illumination levels on the desktop – a great step forward for any light-shy Linux user.