Twilight: Blue light filter

Filters blue light from your screen to reduce digital eye strain and promote better sleep.

Do you struggle to fall asleep? Do your children become restless after using a tablet before bedtime?

Do you frequently use your smartphone or tablet late at night? Do you experience light sensitivity during migraines?

Twilight could be the perfect solution for you!

Recent studies indicate that exposure to blue light before bed can disrupt your natural circadian rhythm, making it harder to fall asleep.

This is due to a photoreceptor in your eyes called melanopsin. This receptor is sensitive to a specific range of blue light (460-480nm), which can suppress the production of melatonin—the hormone that regulates healthy sleep-wake cycles.

Scientific experiments show that an average person reading on a tablet or smartphone for several hours before bed may experience a delay in sleep onset of about one hour. See references below.

The Twilight app adjusts your device's display to the time of day. After sunset, it filters the blue light emitted by your phone or tablet and protects your eyes with a soft, comfortable red filter. The filter's strength automatically adjusts based on your local sunrise and sunset times.

Twilight is also compatible with your Wear OS device.

Documentation

http://twilight.urbandroid.org/doc/

Get More from Twilight

1) Bedtime Reading: Twilight offers a more comfortable viewing experience for nighttime reading. It can reduce screen brightness below the minimum level of your device’s standard controls.

2) AMOLED Screens: After five years of testing on AMOLED screens, Twilight shows no signs of screen burn-in or depletion. When configured correctly, it reduces overall light output (through dimming) and evens out light distribution (by tinting darker areas like the status bar). This may actually help extend your AMOLED screen's lifespan.

Basics on Circadian Rhythm and the Role of Melatonin

http://en.wikipedia.org/wiki/Melatonin

http://en.wikipedia.org/wiki/Melanopsin

http://en.wikipedia.org/wiki/Circadian_rhythms

http://en.wikipedia.org/wiki/Circadian_rhythm_disorder

Permissions

- Location – to determine your local sunrise and sunset times.

- Running Apps – to pause Twilight within selected applications.

- Write Settings – to adjust screen backlight levels.

- Network – to connect with smart lighting (Philips HUE) and filter blue light from your household lights.

Accessibility Service

To extend the filter to your notifications and lock screen, the app may request to enable the Twilight Accessibility Service. This service is used solely to improve screen filtering and does not collect any personal data. Learn more at https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/

Wear OS

Twilight synchronizes the filter settings between your Wear OS watch and your phone. You can control the filter directly from a Wear OS Tile.

Automation (Tasker or Other Tools)

https://sites.google.com/site/twilight4android/automation

Related Scientific Research

Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans – Derk-Jan Dijk & Co, 2012

Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans – Joshua J. Gooley, Kyle Chamberlain, Kurt A. Smith & Co, 2011

Effect of Light on Human Circadian Physiology – Jeanne F. Duffy, Charles A. Czeisler, 2009

Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans – Claude Gronfier, Kenneth P. Wright & Co, 2009

Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans – Kenneth P. Wright, Claude Gronfier & Co, 2009

The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work – Nayantara Santhi & Co, 2008

Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina – Farhan H. Zaidi & Co, 2007