Michael Herf
@mherf.bsky.social
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.
Here is some code, including a Sprague resampler for upsampling spectra (the CIE standard way), if you're into that!
github.com/herf/specwork/
github.com/herf/specwork/
GitHub - herf/specwork: workspace for spectral calcs (f.luxometer + ecological etc.)
workspace for spectral calcs (f.luxometer + ecological etc.) - herf/specwork
github.com
January 25, 2026 at 9:05 PM
Here is some code, including a Sprague resampler for upsampling spectra (the CIE standard way), if you're into that!
github.com/herf/specwork/
github.com/herf/specwork/
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...
www.sciencedirect.com/science/arti...
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…
www.sciencedirect.com
January 25, 2026 at 9:05 PM
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...
www.sciencedirect.com/science/arti...
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...
www.npr.org/2026/01/23/n...
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.
www.npr.org
January 24, 2026 at 6:15 PM
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...
www.npr.org/2026/01/23/n...
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.
December 3, 2025 at 4:26 PM
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.
As well, papers that need blue light to penetrate deep into tissues for the mechanism to work... well blue light doesn't do that.
December 3, 2025 at 4:15 PM
As well, papers that need blue light to penetrate deep into tissues for the mechanism to work... well blue light doesn't do that.
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/...
journals.plos.org/plosbiology/...
journals.plos.org
December 3, 2025 at 4:14 PM
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/...
journals.plos.org/plosbiology/...
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...
www.nature.com/articles/s41...
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
www.nature.com
December 3, 2025 at 4:11 PM
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...
www.nature.com/articles/s41...
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.
Roblox will expand age checks to all users of its communication tools by the end of 2025 using facial age estimation tech, ID verification, and parental consent (Sarah Perez/TechCrunch)
Main Link | Techmeme Permalink
Main Link | Techmeme Permalink
September 4, 2025 at 6:06 PM
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.
👏 Ceiling lamps light up paper but windows light up retinas
August 2, 2025 at 4:44 PM
👏 Ceiling lamps light up paper but windows light up retinas
illustrating how mDFD can apply directly to a dose-response for a "brighter" light
July 30, 2025 at 4:41 PM
illustrating how mDFD can apply directly to a dose-response for a "brighter" light
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...
tvst.arvojournals.org/article.aspx...
Optimizing the Potential Utility of Blue-Blocking Glasses for Sleep and Circadian Health | TVST | ARVO Journals
tvst.arvojournals.org
July 29, 2025 at 6:39 PM
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...
tvst.arvojournals.org/article.aspx...
Reposted by Michael Herf
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...
"It scares me to think of what’s ahead,” Mike Osterholm of CIDRAP told me. www.statnews.com/2025/06/09/r...
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.
www.statnews.com
June 9, 2025 at 9:03 PM
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...
"It scares me to think of what’s ahead,” Mike Osterholm of CIDRAP told me. www.statnews.com/2025/06/09/r...
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.
June 1, 2025 at 6:55 PM
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.
Reposted by Michael Herf
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.
It's not just budgets but research, institutions, expertise, and training the next generation.
May 31, 2025 at 4:43 AM
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.
It's not just budgets but research, institutions, expertise, and training the next generation.
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?
May 9, 2025 at 4:18 PM
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?
It would be cool if AIs only ran on solar because then they’d have circadian rhythm.
May 8, 2025 at 9:39 PM
It would be cool if AIs only ran on solar because then they’d have circadian rhythm.
Astonishing technical feat here, laser projector that tracks eye movements and stimulates cone cells by kind! In just a few milliseconds of latency.
This paper is the result of >20 yrs of hard work by talented students, postdocs and collaborators, but none more than my co-author Ren Ng and his team in EECS.
1/n
Novel color via stimulation of individual photoreceptors at population scale | Science Advances www.science.org/doi/10.1126/...
1/n
Novel color via stimulation of individual photoreceptors at population scale | Science Advances www.science.org/doi/10.1126/...
Novel color via stimulation of individual photoreceptors at population scale
Image display by cell-by-cell retina stimulation, enabling colors impossible to see under natural viewing.
www.science.org
April 23, 2025 at 2:36 PM
Astonishing technical feat here, laser projector that tracks eye movements and stimulates cone cells by kind! In just a few milliseconds of latency.
This is a business model problem. Supporting a niche device for a long time is very expensive.
March 13, 2025 at 7:32 PM
This is a business model problem. Supporting a niche device for a long time is very expensive.
Yet to come, I will post a followup when I have it.
February 12, 2025 at 9:36 PM
Yet to come, I will post a followup when I have it.
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.
February 12, 2025 at 9:33 PM
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.
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.
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.
January 20, 2025 at 6:57 PM
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.
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.
Great article on wildfire smoke, particulates, and VOCs, and how to deal with it:
scienceexchange.caltech.edu/topics/susta...
scienceexchange.caltech.edu/topics/susta...
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.
scienceexchange.caltech.edu
January 19, 2025 at 4:33 AM
Great article on wildfire smoke, particulates, and VOCs, and how to deal with it:
scienceexchange.caltech.edu/topics/susta...
scienceexchange.caltech.edu/topics/susta...
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.
January 12, 2025 at 4:15 PM
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.
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!
January 10, 2025 at 1:57 AM
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!