Twilight: Blue light filter

Are you struggling to fall asleep? Do your children become overly active when using tablets before bedtime? If you frequently use your smartphone or tablet in the evening, or if you're sensitive to light during migraines, Twilight could be the solution you need!

Recent research indicates that exposure to blue light before sleep can disrupt your natural circadian rhythm, making it difficult to fall asleep. This disruption is due to a photoreceptor in your eyes called Melanopsin, which is sensitive to blue light in the 460-480nm range. This sensitivity can suppress the production of Melatonin, a crucial hormone for maintaining healthy sleep-wake cycles. Studies have shown that reading on a tablet or smartphone for a couple of hours before bed can delay sleep by approximately an hour.

Twilight is an app designed to adapt your device's screen to the time of day. It filters out the blue light emitted by your phone or tablet after sunset, replacing it with a soothing red filter that protects your eyes. The intensity of this filter adjusts smoothly based on your local sunset and sunrise times, ensuring a seamless transition.

Twilight is also compatible with Wear OS devices, allowing you to enjoy the same benefits on your smartwatch.

Documentation

Learn more about Twilight at http://twilight.urbandroid.org/doc/

Get More from Twilight

1. Bed Reading: Twilight offers a more comfortable reading experience at night. It can dim the screen backlight far beyond the capabilities of standard screen controls.

2. AMOLED Screens: Our tests on AMOLED screens over five years show no signs of depletion or over-burning. When properly configured, Twilight reduces light emission and promotes a more uniform light distribution, which could extend the life of your AMOLED screen.

Basics on Circadian Rhythm and the Role of Melatonin

Explore more about these topics at:

• 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 current sunset and sunrise times.
• Running Apps: To disable Twilight in selected apps.
• Write Settings: To adjust the backlight.
• Network: To access smart lighting systems like Philips HUE to reduce blue light in your household.

Accessibility Service

To filter notifications and lock screens, Twilight may request the enabling of its Accessibility Service. This service is used solely to enhance screen filtering and does not collect any personal information. For more details, visit 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, and you can control filtering through a "Wear OS Tile".

Automation (Tasker or Other)

Discover automation options at 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