f.lux

Ordinary background light comes in different colours depending on the source. Sunlight produces one tint and indoor lighting another. f.lux is an interesting utility for anyone who has to use a computer into the night. It adjusts the colours you see on screen to complement the kind of light that is expected given the time of day.

This version is for Windows but there are also versions available for Mac and Linux.

In order for f.lux to work properly it must be told the kind of lighting you have near the computer, as well as your latitude. You can use the built-in search tool to find the latitude.

The software can be disabled temporarily, which is useful if you have to do any work, such as photo editing, that depends on viewing more accurate colours . The exact colour adjustment can also be changed if the default isn't to your liking.

One small flaw is that it doesn't work properly in the southern hemisphere.