Twilight: Blue light filter

Are you struggling to fall asleep at night? Do your children become hyperactive after using tablets before bedtime? If you use your smartphone or tablet in the evening or are sensitive to light during migraines, Twilight could be the perfect solution for you.

Recent scientific research indicates that exposure to blue light before sleep can disrupt your natural circadian rhythm, making it harder to fall asleep. This issue stems from 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, a crucial hormone for maintaining healthy sleep-wake cycles. Studies have shown that reading on a tablet or smartphone for a few hours before bed can delay sleep by about an hour.

Twilight is designed to help mitigate these effects by adapting your device's screen to the time of day. It filters out blue light from your phone or tablet after sunset, replacing it with a soothing red filter. The intensity of this filter adjusts smoothly according to your local sunset and sunrise times, ensuring a natural transition.

You can also use Twilight on your Wear OS device, syncing the filter settings with your phone for a consistent experience.

Documentation

For more detailed information, visit Twilight's documentation page.

Enhance Your Experience with Twilight

1. Bedtime Reading: Twilight offers a more comfortable reading experience at night, capable of dimming the screen backlight far below the standard settings.

2. AMOLED Screens: Extensive testing on AMOLED screens shows that Twilight can be used for up to 5 years without causing screen depletion or over-burning. When properly configured, Twilight reduces light emission and provides a more uniform light distribution, potentially extending the life of your AMOLED screen.

Understanding Circadian Rhythms and Melatonin

To learn more about circadian rhythms and the role of Melatonin, check out these resources:

• Melatonin
• Melanopsin
• Circadian Rhythms
• Circadian Rhythm Disorders

Permissions Required

Twilight requires the following permissions to function optimally:

• 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 Access: To connect with smart lights like Philips HUE to reduce blue light in your household.

Accessibility Service

To filter your notifications and lock screen, Twilight may request access to its Accessibility Service. This service is used solely to enhance screen filtering and does not collect any personal data. Learn more about this at Twilight's privacy information page.

Wear OS Integration

Twilight syncs with your Wear OS device, allowing you to control the filter settings directly from a "Wear OS Tile."

Automation with Tasker

For advanced users, Twilight supports automation through Tasker and other platforms. Find out more at Twilight's automation guide.

Related Scientific Research

Several studies support the efficacy of reducing blue light exposure:

• "Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans" by Derk-Jan Dijk, et al. (2012)
• "Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans" by Joshua J. Gooley, et al. (2011)
• "Effect of Light on Human Circadian Physiology" by Jeanne F. Duffy and Charles A. Czeisler (2009)
• "Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans" by Claude Gronfier, et al. (2009)
• "Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans" by Kenneth P. Wright, et al. (2009)
• "The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work" by Nayantara Santhi, et al. (2008)
• "Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina" by Farhan H. Zaidi, et al. (2007)