Twilight: Blue light filter

Struggling to fall asleep? Noticed your kids are overly active after using their tablet before bedtime? If you're using your smartphone or tablet late in the evening, or if you're sensitive to light during migraines, Twilight might just be the solution you need!

Recent research highlights that exposure to blue light before sleep can disrupt your natural circadian rhythm, making it harder to drift off. 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 Melatonin production, 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 about an hour.

The Twilight app dynamically adjusts your device's screen to the time of day, filtering out blue light post-sunset and applying a soothing red filter to protect your eyes. This filter's intensity adjusts smoothly based on your local sunrise and sunset times, ensuring optimal viewing comfort.

Twilight is also compatible with Wear OS devices, enhancing your overall experience by syncing your smartwatch's screen with your phone's settings.

Documentation

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

Get More from Twilight

1) Bed Reading: Twilight offers a more comfortable night reading experience, allowing the screen's backlight to be dimmed far beyond the capabilities of standard controls.

2) AMOLED Screens: Our tests on AMOLED screens over five years show no signs of depletion or over-burning. With proper configuration, Twilight reduces light emission through dimming and provides a more uniform light distribution, potentially extending your AMOLED screen's lifespan.

Basics on Circadian Rhythm and the Role of Melatonin

For further reading on these topics, visit:

• 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

Twilight requires the following permissions:

• Location: To determine your current sunset and sunrise times.
• Running Apps: To disable Twilight in selected applications.
• Write Settings: To adjust the screen's backlight.
• Network: To access smart lighting (Philips HUE) to shield your household light from blue light.

Accessibility Service

To extend filtering to notifications and the lock screen, Twilight may request access to its Accessibility Service. Rest assured, this service is used only to enhance screen filtering and does not collect any personal data. Learn more about this 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, and you can manage the filtering through a "Wear OS Tile".

Automation (Tasker or Other)

For automation details, visit https://sites.google.com/site/twilight4android/automation.

Related Scientific Research

Explore the impact of light on sleep and circadian rhythms in these studies:

• 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)