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iPhone you turn on the red light

As detailed here and shown below you can use iOS’s >10 accessibility settings colour filters to modify the screen to emit a red (or other colour) rather than the main or night shift offering. Pair it with a single accessibility shortcut and we’ve got a quick way -three quick taps on the home or side buttons- to trigger this display light modification.

How to Turn it On

*click* CONTINUED for detailed exploration

In my own personal usage I’ve noticed:


  • Casts far less luminance (not as obvious or distracting from a distance) especially useful in any dark space where the light emanating from the device is (a) distraction/prohibited
  • It ‘feels’ less harsh on my eyes –I think?
  • It’s fun to show people and talk about


  • The red backlit colour makes whites look red so anything white and red looks JUST red which makes notification bubbles basically unreadable.
  • People definitely notice the screen close up cause it’s so different (if you don’t like to talk about it ; )

Dark Adaptation

The main advantage in shifting your display’s colour is that the red screen may keep one’s eyes “dark adapted” an adaptation by the human eye that renders the dark time more vibrant and alive than our over-exposed sun-eyes could render. See Brian Koberlein’s explanation for more specific details. In short: rods and cones responding differently to different amounts and colours of light, over expose your eyes while adapted and you’ll need at least another 30mins to get back in the dark zone.

Now, as mentioned in the post, if the light from the iPhone’s red screen exceeds 650 nanometers you’ll lose your dark adaptation and make the red light tuning redundant. So the essential question: what is the output from the iPhone’s screen across different models and with the red light filter on? Specifically is their a maximum brightness one could have the screen at to get this dark adapted preservation advantage -OR- perhaps the iPhone’s light even at minimum brightness exceeds the nanometers measurement we’d need to maintain? 

… more soon




  1. Bruce wrote:

    I recall you messing with that at WiseClub last year!

    Wednesday, January 10, 2018 at 3:14 pm | Permalink
  2. jason wrote:

    Year for sure! Access to the feature has definitely improved with assigning one accessibility shortcut! I do still like it quite a bit.

    Thursday, January 11, 2018 at 3:10 pm | Permalink

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