Twilight: Blue light filter

Are you struggling to fall asleep at night? Do your children become hyperactive 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 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. This light can suppress the production of Melatonin, a 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 soothing red filter to protect your eyes. The intensity of the filter smoothly adjusts based on your local sunset and sunrise times. Twilight is also compatible with Wear OS devices.

For more detailed information, visit the Twilight documentation.

Here are some additional benefits of using Twilight:

1) Bed Reading: Twilight provides a more comfortable reading experience at night, allowing you to 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. When properly configured, Twilight reduces light emission and ensures a more even light distribution, potentially extending the life of your AMOLED screen.

To understand more about circadian rhythms and the role of melatonin, you can refer to these resources:

• Melatonin
• Melanopsin
• Circadian Rhythms
• Circadian Rhythm Disorder

Twilight requires the following permissions to function effectively:

• Location - to determine your local sunset and sunrise times.
• Running apps - to disable Twilight in selected applications.
• Write settings - to adjust the screen backlight.
• Network - to connect with smart lighting systems like Philips HUE to reduce blue light in your home environment.

To filter notifications and the lock screen, Twilight may request the use of the Twilight Accessibility Service. This service is used solely to enhance screen filtering and does not collect any personal data. For more information on privacy, visit this link.

Twilight also syncs with your Wear OS device, allowing you to control the filter settings via a "Wear OS Tile". For automation options, including integration with Tasker, check out this guide.

For those interested in the scientific basis behind Twilight, here are some related 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