Twilight: Blue light filter

Are you struggling to fall asleep? Do your kids seem overly energetic after playing with their tablets before bedtime? If you're using your smartphone or tablet in the late evening or if you're sensitive to light during migraines, Twilight might 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 is due to a photoreceptor in your eyes called Melanopsin, which is sensitive to blue light in the 460-480nm range. Such exposure can suppress the production of Melatonin, the hormone crucial 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 about an hour.

The Twilight app adjusts your device's screen to the time of day, filtering out blue light after sunset and applying a soft, pleasant red filter to protect your eyes. This filter's intensity smoothly transitions based on your local sunrise and sunset times.

Twilight is also compatible with your Wear OS device, ensuring consistent screen filtering across your gadgets.

Documentation

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

Get More from Twilight

1) Bed Reading: Twilight provides a more comfortable reading experience at night, allowing the screen backlight to be dimmed far below what's possible with standard screen controls.

2) AMOLED Screens: Extensive testing on AMOLED screens over five years shows no signs of depletion or over-burning. When properly configured, Twilight reduces light emission through dimming while evenly distributing light (tinting darker areas like the status bar), which may extend your AMOLED screen's lifespan.

Basics on Circadian Rhythm and the Role of Melatonin

Explore further with these resources:

• 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: Used to determine your local sunset and sunrise times.
• Running Apps: Allows Twilight to pause in selected apps.
• Write Settings: Required to adjust the backlight.
• Network: Accesses smart light systems (like Philips HUE) to filter blue light from your household lighting.

Accessibility Service

To filter notifications and the lock screen, Twilight may request access to its Accessibility Service. Rest assured, the app uses this service solely to enhance screen filtering and does not collect any personal data. For more information, visit https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/.

Wear OS

Twilight syncs with your Wear OS device, applying the same filter settings as your phone. Control filtering directly from a "Wear OS Tile".

Automation (Tasker or Other)

For more on automation, check out 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