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Michael Herf

@mherf

I make f.lux (lighting and screens) and do research on sleep and circadian neuroscience, color, and vision. Previously: Picasa (founding CTO), Google, MetaCreations, Microsoft, CMU.

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28.12.2023
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Latest posts by Michael Herf @mherf

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Bipolar mood cycles and lunar tidal cycles - Molecular Psychiatry Molecular Psychiatry - Bipolar mood cycles and lunar tidal cycles

If you're interested in that one, Tom Wehr's work is also good, though it's mainly in bipolar individuals: www.nature.com/articles/mp2...

05.03.2026 17:03 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
Europe PMCEurope PMC Europe PMC is an archive of life sciences journal literature.

"Lunar gravity predicts sleep timing" - bookmarking this lunar rhythms & sleep paper as interesting. It uses a 30-day rhythm but not the 28-day declination rhythm - a claim of "gravity" should probably use the 28-day one, but I think "phase" should follow 30?

europepmc.org/article/med/...

05.03.2026 17:02 πŸ‘ 0 πŸ” 1 πŸ’¬ 1 πŸ“Œ 0

I think yes, 8AM could be <CBTmin if you've been up in moderately bright light until 4AM. Teens are starting from a late phase already - the amazing thing with this graph is that it is *all of them*.
Wonder if teens have a larger CBTmin-DLMO phase angle compared to adults?

27.02.2026 00:52 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Amazing data here - just 100lux of room light while staying up late seems to delay teens enough that 8000lx of morning bright light delays them further:

26.02.2026 19:47 πŸ‘ 7 πŸ” 2 πŸ’¬ 1 πŸ“Œ 0
GitHub - herf/specwork: workspace for spectral calcs (f.luxometer + ecological etc.) workspace for spectral calcs (f.luxometer + ecological etc.) - herf/specwork

Here is some code, including a Sprague resampler for upsampling spectra (the CIE standard way), if you're into that!
github.com/herf/specwork/

25.01.2026 21:04 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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Assessing and mapping taxon-specific effects of ecological light pollution for environmental impact analysis Predicting the adverse effects of light at night is necessary to ensure compliance with laws and regulations that protect species. Using two case stud…

I helped Travis with some moonlight calcs for this paper - our code figures out "how bright compared to moonlight is this light for each species". There is a ton of photometrics and spatial modeling here too:
www.sciencedirect.com/science/arti...

25.01.2026 21:04 πŸ‘ 5 πŸ” 1 πŸ’¬ 1 πŸ“Œ 0
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How cuts to federal climate funds could threaten polar vortex research Tens of millions of people are in the path of a major winter storm. Federal cuts threaten efforts to understand the causes of such weather.

When the cold fronts come farther south, I search for the latest in polar vortex research. This time:

www.npr.org/2026/01/23/n...

24.01.2026 18:15 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

They try to help teens by pulling out the 10% worst of social media… while leaving the five hours a day of not sleeping or socializing, as if that stuff doesn’t matter.

03.12.2025 16:26 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

As well, papers that need blue light to penetrate deep into tissues for the mechanism to work... well blue light doesn't do that.

03.12.2025 16:15 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Lots of higher-quality older work that says the closer to green you get, the more you induce sleep/torpor. And also that mice experience "aversion" to blue light and reduce activity. So shining bright blue on mice is not a good model of people or mitochondria.

journals.plos.org/plosbiology/...

03.12.2025 16:13 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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Impact of short wavelength light exposure on body weight, mobility, anxiety like behaviour and cytokine expression - Scientific Reports Scientific Reports - Impact of short wavelength light exposure on body weight, mobility, anxiety like behaviour and cytokine expression

Some notes on "blue light harms mitochondria" making the rounds this week - a lot of the evidence is VERY indirect like this paper that says mice in blue light gain weight. 1/n

www.nature.com/articles/s41...

03.12.2025 16:11 πŸ‘ 2 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Facial age estimation requires a 5-7 year margin of safety in validation studies, so when the software says you're 23-25 you can be considered 18. Errors are even larger around age 13, so basically useless for distinguishing minors from adults.

04.09.2025 18:06 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 1

πŸ‘ Ceiling lamps light up paper but windows light up retinas

02.08.2025 16:44 πŸ‘ 1 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0
Post image

illustrating how mDFD can apply directly to a dose-response for a "brighter" light

30.07.2025 16:41 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
Optimizing the Potential Utility of Blue-Blocking Glasses for Sleep and Circadian Health | TVST | ARVO Journals

We proposed a new metric (mDFD) for blue-blocking glasses. It's based on the sensitivity of melanopsin, log-transformed to resemble optical density:

tvst.arvojournals.org/article.aspx...

29.07.2025 18:39 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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Health secretary RFK Jr. abruptly fires CDC vaccine advisory panel Health secretary Robert F. Kennedy Jr. has taken the extraordinary step of firing the expert panel that advises the CDC.

This is the big one: Kennedy is firing the entire #ACIP in a move he says is needed to restore confidence in vaccines.
"It scares me to think of what’s ahead,” Mike Osterholm of CIDRAP told me. www.statnews.com/2025/06/09/r...

09.06.2025 21:03 πŸ‘ 266 πŸ” 134 πŸ’¬ 22 πŸ“Œ 38

It's troubling that LLMs do not represent probability distributions *at all* - if you ask a question that should have a normal distribution, it will pick almost the same number every time. Maybe it's the mean, who knows - but it isn't equipped to reason about human populations this way.

01.06.2025 18:55 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
Graphs showing 25 years of budgets for the National Institute of Health, NASA, and the NSF. In all cases, the proposed budget for next year is far, far below any year of the previous quarter century.

Graphs showing 25 years of budgets for the National Institute of Health, NASA, and the NSF. In all cases, the proposed budget for next year is far, far below any year of the previous quarter century.

There are 2 previous historical cases of countries destroying their science and universities, crippling them for decades: Lysenkoism in the USSR and Nazi Germany. The Trump administration will be the 3rd.
It's not just budgets but research, institutions, expertise, and training the next generation.

31.05.2025 04:43 πŸ‘ 15226 πŸ” 7877 πŸ’¬ 454 πŸ“Œ 531

Agreeing that we need better names, I would add that it bugs me when people say the human L-cone peak is "red". It looks to me much more like "yellow", and then it's only via L-M opponency that we get the "red" color response?

09.05.2025 16:18 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

It would be cool if AIs only ran on solar because then they’d have circadian rhythm.

08.05.2025 21:39 πŸ‘ 2 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0

Astonishing technical feat here, laser projector that tracks eye movements and stimulates cone cells by kind! In just a few milliseconds of latency.

23.04.2025 14:36 πŸ‘ 3 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0

I am so sorry. πŸ’”

01.04.2025 05:06 πŸ‘ 5 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

This is a business model problem. Supporting a niche device for a long time is very expensive.

13.03.2025 19:32 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Yet to come, I will post a followup when I have it.

12.02.2025 21:36 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Just received word that ANSI has approved our "flicker" TM, (ANSI/IES TM-39-25), which addresses in delightful detail how flickering lights of all kinds affect people. Congrats to everyone involved with the IES Vision Science Committee.

12.02.2025 21:33 πŸ‘ 3 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Same concern as this post:
PurpleAir (highly rated by AQMD) and IQAir are reporting 500% the AQI of the single reference sensor. This is the "reference" sensor used by everyone near the Palisades fire, and surely it should not be.

20.01.2025 18:56 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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Ask a Caltech Expert: Paul Wennberg on Environmental Hazards of Smoke Paul Wennberg discusses the air quality following the 2025 California fires and how to clean homes downwind of the fires.

Great article on wildfire smoke, particulates, and VOCs, and how to deal with it:

scienceexchange.caltech.edu/topics/susta...

19.01.2025 04:33 πŸ‘ 2 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0

If you’re in an area affected by fires, turning up your car’s fan helps with air quality - cabin air filters are pretty decent.

12.01.2025 16:15 πŸ‘ 5 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0

Friend called me "we've been evacuated from the fires but can't see our security cameras" - tried @tailscale.com on a pi for the first time and they had a VPN in 20 minutes later. Thanks for the free version!

10.01.2025 01:57 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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Is your iPhone sharing photos data with Apple by default? It is, but you can change it.

There should be a privacy panel of regular people who can go deep on privacy-related defaults and explain it. If 90% of them vote yes, you can turn it on by default. e.g., this is pretty defensible IMO (but not obvious why at first glance):

www.theverge.com/2024/12/29/2...

05.01.2025 17:21 πŸ‘ 4 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0