Twilight: Blue light filter

Struggling to fall asleep? Are your kids overly energetic after playing on their tablets before bedtime? If you're using your smartphone or tablet in the evening or are sensitive to light during migraines, Twilight could be the perfect solution for you.

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

The Twilight app adjusts your device's screen to the time of day, filtering out blue light emitted by your phone or tablet after sunset. It uses a soothing red filter that not only protects your eyes but also adjusts smoothly based on your local sunrise and sunset times.

Twilight is also compatible with Wear OS devices, ensuring a consistent experience across your gadgets.

Documentation

For more detailed information, visit: http://twilight.urbandroid.org/doc/

Get More from Twilight

1) Bed Reading: Twilight enhances the night reading experience by allowing you to dim the screen far below the standard backlight controls, making it more comfortable for your eyes.

2) AMOLED Screens: Extensive testing on AMOLED screens over five years has shown no signs of depletion or over-burning. With proper configuration, Twilight reduces light emission and ensures an even light distribution, potentially extending the lifespan of your AMOLED screen.

Basics on Circadian Rhythm and the Role of Melatonin

For a deeper understanding, check out these resources:

• Melatonin
• Melanopsin
• Circadian Rhythms
• Circadian Rhythm Disorder

Permissions

• Location: To determine your local sunset and sunrise times.
• Running Apps: To pause Twilight in selected apps.
• Write Settings: To adjust the screen backlight.
• Network: To connect with smart lights (like Philips HUE) to shield your household from blue light.

Accessibility Service

To filter your notifications and lock screen, Twilight may request to enable its Accessibility Service. This service is used solely to enhance 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 syncs your Wear OS screen with your phone's filter settings, allowing you to control filtering directly from a "Wear OS Tile".

Automation (Tasker or Other)

For automation features, visit 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