Cell phone screens emit more than 10 lux of light even when turned to the darkest setting.
Posted by The Charlie Kirk Show, Checked
- Sources
- 1 contradict1 support3 context
- Said
- 1 time·
- Confidence
- 50%
The Charlie Kirk ShowAug 5, 2026
The sources support that phone screens emit more than 10 lux in ordinary nighttime use (Stanford reports 25-50 lux under usual conditions), but nothing directly measures the darkest setting. One unrated source reports that phones at minimum brightness may deliver under 10 lux, which cuts against the 'even at darkest setting' part of the claim.
This claim is about the present, so it is judged as of the day it was checked.
What was said
… to get pregnant and she just wants to make sure everything's, you know, her circadian rhythms are, are right, what time do you recommend stop, you know, stopping the scrolling? I mean, the science is 10 lux and below the three hours leading up to bedtime, so you get more than ten lux off your cell phone screen, even if you turn it all the way dark, and you get the blue light. Yeah, you get blue light. You get that lux. I mean, and that is enough to keep the brain making cortisol and restart, kickstart that sex steroid hormone pathway at night, which is the opposite of what we want. …
The Charlie Kirk Show · · from the transcriptPost →What we found
Contradicts. A search-based analysis reports that at minimum brightness settings phones may deliver under 10 lux, which conflicts with the claim that the darkest setting still exceeds 10 lux. This source is unrated and hedged.[2]
Supports. Stanford Lifestyle Medicine reports that phone screens emit 25-50 lux under usual conditions at night, which is above the 10-lux threshold in ordinary use.[1]
Context. A 2015 Nature study measured smartphone circadian illuminance at 100% brightness in a dark room and found values above 41 biolux, but it did not test the minimum or darkest setting.[3]
Context. Luminance and illuminance figures vary widely with distance, brightness setting, and device, so no single source settles the darkest-setting figure.[2][4][5]
Sources
5 sources: 1 primary, 3 not rated, 1 tier 1
- 1Screen Time and Sleep—It's Different for Adultslifestylemedicine.stanford.edu · primary source · cited for: supports
- 2PROVED: Smartphone screens deliver ~80-100 lux (vs. sunlight ~100,000 lux), posing negligible blue-light risk for retinal damage or macular degeneration, but evening use suppresses melatonin via ipRGCs/melanopsin and delays sleep onset by up to 90 minutes.proofengine.info · not rated · cited for: contradicts, context
- 3Analysis of circadian properties and healthy levels of blue ...nature.com · tier 1 · cited for: context
- 4Light Converter - Lux, Lumens, Candela and Foot-Candles - syntelabsyntelab.com · not rated · cited for: context
- 5Apple iPhone 17 Pro Max Display testdxomark.com · not rated · cited for: context
Where this claim was made
Said in 1 published post
Related claims
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- Women's menstrual cycles became irregular in 2010 because of the introduction of smartphones and artificial light at night.Mixed
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