Twilight: Blue light filter

Filters blue light from your screen to reduce eye strain and improve sleep quality.

Do you struggle to fall asleep at night? Do your children become overly active after using a tablet before bedtime?

Do you frequently use your smartphone or tablet late in the evening? Do bright screens bother you during migraines?

Twilight could be the perfect solution for you!

Current research indicates that blue light exposure before bed can disrupt your natural circadian rhythm and make it harder to fall asleep.

This occurs because of melanopsin, a photoreceptor in your eyes that's particularly sensitive to blue light in the 460-480nm range. This sensitivity can suppress melatonin production—the hormone that regulates healthy sleep-wake cycles.

Scientific studies demonstrate that people who read on tablets or smartphones for several hours before bed typically experience sleep delays of approximately one hour. See references below.

The Twilight app adjusts your device's display to match the time of day. After sunset, it filters blue light from your phone or tablet and applies a comfortable red tint to protect your eyes. The filter intensity automatically adjusts according to local sunrise and sunset times.

Twilight is also compatible with Wear OS devices.

Documentation

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

Get More from Twilight

1) Bedtime Reading: Twilight creates a more comfortable reading experience at night by reducing screen brightness beyond what standard backlight controls allow.

2) AMOLED Screens: After five years of testing on AMOLED displays, Twilight shows no signs of screen burn-in or degradation. When configured properly, it reduces overall light emission through dimming and ensures more uniform light distribution, potentially extending your AMOLED screen's lifespan.

Understanding Circadian Rhythm and 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 - Determines local sunset and sunrise times

- Running Apps - Allows Twilight to pause during specific applications

- Write Settings - Adjusts backlight levels

- Network - Controls smart lighting (Philips HUE) to reduce blue light in your home environment

Accessibility Service

To extend filtering to notifications and lock screens, Twilight may request Accessibility Service access. This service only enhances screen filtering and doesn't collect personal data. Learn more at https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/

Wear OS

Twilight synchronizes your Wear OS display with your phone's filter settings. Manage filtering directly through the Wear OS Tile.

Automation (Tasker and Others)

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