ELi5: Why do phones have blue light filters? What are those blue filters actually doing and or helping? Furthermore, should we be watching ‘blue light levels’ from other devices like TVs, monitors, etc?



I think this might be a blend of the technology/engineering/biology flairs, hopefully I made this post correctly!

In: Technology

Research has shown that blue light specifically causes our body to produce less melatonin, which is the hormone our body uses to help us sleep and help regulate our natural biological clock.

Staring at screens – TV, computer monitors, phones, tablets, etc. – exposes us to colors from *all* of the visible light spectrum, but it’s the wave length of blue light specifically that has this effect. That’s why you can see things like blue light filtered glasses and why your “night time” mode on your computer turns the screen orange and stuff.

Our brains use blue light to help regulate our sleep patterns – when you have a large amount of blue light, your brain sends signals to your body to stay awake.

Historically, this wasn’t an issue, as the only real natural source of blue light is the sun itself. However, with the advent of modern electronics devices, we are getting blue light at all hours of the day (looking at your phone after dark) and it is causing sleep issues. The blue light filters on phones are meant to help resolve this by limiting our blue light after dark.

We should be watching blue light levels from other devices as well – most sleep doctors recommend you stop watching TV at least an hour before you go to bed to so your body stops sending ‘stay awake’ signals that can disrupt sleep.

The initial thought process was that we thought blue light stimulates brain activity or something like that. So phones started coming equipped with blue light filters so that later at night you could turn that on and in theory that would help you fall asleep better after you were done, as opposed to without the blue light filter your brain activity would be stimulated and you’d have a tough time falling asleep.

But new research is indicating the blue light doesn’t have the effect on brain waves that we thought it does so at this point blue light filters are for all intents and purposes essentially useless and really only serve to skew the color of your display.

Thanks all, this was super helpful! Much appreciated!