Twilight: Blue light filter

Are you struggling to fall asleep at night? Do your children seem overly energetic after using tablets before bedtime? If you're using your smartphone or tablet in the evening or are 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 harder 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. 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 couple of hours before bed can delay sleep by about an hour.

Twilight is an app designed to help by adapting your device's screen to the time of day. It filters out blue light emitted by your phone or tablet after sunset, replacing it with a soothing red filter. The intensity of this filter adjusts smoothly based on your local sunset and sunrise times, ensuring a comfortable viewing experience that's easier on your eyes.

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

Documentation

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

Get More from Twilight

1. Bed Reading: Twilight enhances the night reading experience by making it more pleasant on the eyes. It can dim the screen beyond the capabilities of standard backlight controls.

2. AMOLED Screens: Extensive testing on AMOLED screens over five years shows no signs of depletion or over-burning. Properly configured, Twilight reduces light emission and ensures a more even light distribution, potentially extending your screen's lifespan.

Basics on Circadian Rhythm and the Role of Melatonin

To learn more about these topics, check out these resources:

• Melatonin
• Melanopsin
• Circadian Rhythms
• Circadian Rhythm Disorder

Permissions

Twilight requires the following permissions to function effectively:

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

Accessibility Service

To filter notifications and the lock screen, Twilight may request the use of its Accessibility Service. This service is used solely to enhance screen filtering and does not collect any personal information. For more details, visit Twilight's privacy information page.

Wear OS

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

Automation (Tasker or Other)

For advanced users, Twilight supports automation through tools like Tasker. Learn more at Twilight's automation page.

Related Scientific Research

For those interested in the science behind Twilight, here are some key studies:

• "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

By using Twilight, you can reduce blue light exposure, minimize eye strain, and improve your sleep quality. Give it a try and see the difference it can make!