Twilight: Blue light filter

Are you struggling to fall asleep or noticing that your kids are overly energetic after using tablets before bedtime? Are you sensitive to light, especially during migraines, or do you often use your smartphone or tablet in the evening? Twilight could be the solution you're looking for!

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 the photoreceptor in your eyes known as Melanopsin, which is sensitive to blue light in the 460-480nm range. This light 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.

Twilight helps by adapting your device's screen to the time of day. It filters out blue light emitted by your phone or tablet after sunset, using a soft and pleasant red filter. The intensity of the filter adjusts smoothly based on your local sunset and sunrise times, ensuring a seamless transition. Additionally, Twilight is compatible with Wear OS devices.

For more details, check out the documentation at http://twilight.urbandroid.org/doc/.

Get More from Twilight

1. Bed Reading: Twilight offers a more eye-friendly experience for night reading. It can dim the screen far below the standard backlight controls, making it perfect for late-night reading.

2. AMOLED Screens: Our tests show that Twilight, when properly configured, can extend the life of AMOLED screens. By enabling dimming and providing a more even light distribution, it may actually increase the longevity of your screen.

Basics on Circadian Rhythm and Melatonin

Learn more about the science behind sleep and light 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

Twilight requires the following permissions:

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

Accessibility Service

To filter notifications and the lock screen, 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. 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 through a "Wear OS Tile".

Automation (Tasker or Other)

For automation options, 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 & 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 & Co, 2009
• Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans - Kenneth P. Wright & 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