Adjust screen brightness automatically at night

One app to try

f.lux™ Better lighting...for your computer

it makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day.

Available for XP/Vista/7, OSX and linux

None of the currently suggested solutions actually change the brightness of the monitor automatically at night. Especially if you are on a desktop setup changing the brightness of each of your monitors is a pain.

This utility from Nirsoft allows you to change monitor variables from the command line. By creating a tasks in Windows' Task Scheduler to run at a certain times you could set your monitors brightness to progressively lower values.

However that solution is not completely seamless. If you're OK with using freeware to solve this issue, ClickMoniterDDC is a GUI that can change the brightness of monitors at certain times and far more.

You can use Dimmer for Windows to lower the brightness itself between 5% and 95% opacity.

f.lux is great, but it just doesn't do enough; you can use it in combination with Dimmer, though.

Redshift adjusts the color temperature of your screen according to your surroundings. This may help your eyes hurt less if you are working in front of the screen at night.

By default Redshift does not directly dim the picture, but instead shifts the color into red. We can disable the color shifting by using -t 6500:6500 as parameter. Additionally, with -b we can set the brightness of the image to use, for example -b 0.8:0.1 will dim the image from 0.8 during the day, to 0.1 during the night.

Of course, all this does not change the settings of the monitor itself, it can only adjust the image that is being send to monitor. If your monitor is configured to be too bright, even a dark gray might be too bright in the night.