f.lux | PCWorld

Have you ever gone by a house where the TV was on at night, andnoticed the bluish glow emanating from the screen? Or woken upearly and switched on your monitor (or smartphone) to be blinded bya burst of bright white light? With f.lux, this doesn’t haveto happen.

It turns out monitor brightness isn’t the only thing toblame when this happens. Color temperature, measured in unitscalled kelvin, has a lot to do with it. The simplest way to explaincolor temperature is in terms of tint: You know how the color whitesometimes seems “warm” (a bit reddish) and sometimes“cool” (bluish)? That’s color temperature atwork.

With their typical cool tint, computer monitors look greatduring daytime hours. But once the sun sets, monitor screens lookmuch better if their color temperature is adjusted accordingly. Andthat’s what f.lux does.

F.lux takes your location and the current date into account, andcan tell when the sun is going to set every day. Right around thattime, with F.lux running in the background, you will notice a“virtual sunset” happening on your monitor. Everythingseems to mellow down a little bit, every shade of color growingslightly warmer and cozier than it was during the day.

You can set the adjustment to happen very gradually over thecourse of a full hour, or quickly (in twenty seconds). When usingthe fast adjustment option, things visually slow down while theadjustment is being done, but it only takes a moment. Adjusted, themonitor looks completely natural, and after a while you may evenforget the color temperature was ever changed.

If you’re doing color-sensitive work, you may want todisable f.lux temporarily. Unfortunately, you can disable it foronly one hour--no more, no less. If you need to disable it for morethan an hour, you simply have to quit the app (and then may forgetto switch it back on--that's what often happens to me, atleast).

According to research paperscited on the Flux website, insomnia may be linked to blue light.There is no conclusive evidence on this, but many practitionersrecommend avoiding blue light within two hours of sleep.

After working with f.lux for over a year, I can say that itmakes it easier for me to go to sleep at night after spending sometime in front of the screen. If I could just disable it for morethan an hour at a time, it would be just about perfect.

--Erez Zukerman

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