Twilight: Blue light filter

Filter blue light from your screen, reduce eye strain, and improve your sleep.

Are you struggling to fall asleep? Do your children become hyperactive after using tablets before bed? Do you frequently use your smartphone or tablet late at night? Are you light-sensitive during migraines? Twilight might be the solution! Recent research indicates that blue light exposure before sleep disrupts your natural circadian rhythm, hindering sleep. This is due to melanopsin, a photoreceptor in your eyes sensitive to blue light (460-480nm), which suppresses melatonin production—a hormone crucial for healthy sleep-wake cycles. Studies show that reading on a tablet or smartphone for a couple of hours before bed can delay sleep by about an hour. See references below.

The Twilight app adapts your device's screen to the time of day. It filters blue light emitted after sunset, protecting your eyes with a soft red filter. Filter intensity adjusts smoothly based on your local sunrise and sunset times. You can also use Twilight on your Wear OS device.

Documentation: http://Twilight.urbandroid.org/doc/

Get More from Twilight:

1. Bedtime Reading: Twilight is gentler on the eyes for night reading, dimming the backlight far beyond your device's built-in controls.
2. AMOLED Screens: Five years of testing on AMOLED screens show no sign of depletion or burn-in. Properly configured, Twilight reduces light emission (through dimming) and provides more even light distribution (tinting dark areas like the status bar). This may even extend your AMOLED screen's lifespan.

Basics on Circadian Rhythm and Melatonin's Role:

• 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 sunset/sunrise times.
• Running Apps: To pause Twilight in specific apps.
• Write Settings: To adjust backlight.
• Network: To access smart lighting (Philips HUE) for blue light reduction in your home.

Accessibility Service:

To filter notifications and the lock screen, the app may request access to the Twilight Accessibility Service. This is solely for improved screen filtering and does not collect personal information. Learn more: https://Twilight.urbandroid.org/is-Twilights-accessibility-service-a-thread-to-my-privacy/

Wear OS: Twilight syncs your Wear OS screen with your phone's filter settings. Control filtering via a "Wear OS Tile".

Automation (Tasker or similar): 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