If your eyes often feel tired after a lengthy session on your PC then one possible explanation is that your display isn’t using an appropriate colour temperature. Monitors will be typically be set very high, which may be fine in bright daylight, but is less appropriate for night-time viewing (and may, some suggest, even contribute to sleeping problems).

You don’t have to put up with this, though. Not with a little help from F.lux, a simple free program which uses your location, the date and time of day to figure out your sunrise and sunset times, then automatically adjusts your monitor’s temperature to an appropriate level.

What does this mean? We weren’t quite sure, but it’s surprisingly easy to find out. Just launch F.lux, click the icon representing the sun, and the program will cycle through its various stage: a high colour temperature for a blue brightness during the day, changing to a softer yellow-orange glow at night.

It has a few basic options, but otherwise F.lux works entirely automatically

At first this will look far too drastic, but that’s because you’re viewing it all at once, and at the same time of day. In real life the results are far more acceptable, and there’s a good chance that your eyes will not only adjust, but that you’ll find the new scheme much more comfortable for lengthy PC viewing.

If you’re not happy with the effect, though, clicking “Change Settings” allows you to customise it in various ways. You can set your location more precisely, for instance; define exactly which colour temperature you’d like to use for day and night work; and choose how quickly the program shifts from one temperature to another. (By default this is distractingly quick – we’d recommend you choose the “Slow” option.)

F.lux won’t be for everyone. If your ambient lighting doesn’t change much (you’re in an office with no windows, say), you’ll probably be better off setting your monitor colour temperature to an appropriate level, and leaving it there. And if you regularly do design work where you need 100% colour accuracy and consistency, then having them change like this probably won’t be helpful. (Although the program does include a “Disable” option for when you need to do colour-critical work.)

If your lighting is a little more variable, though, and your PC is used mostly for browsing, email and similar tasks, then F.lux could prove a simple and straightforward way to ensure your monitor is always at its most appropriate, comfortable-to-read settings.