Is Flicker Dangerous in Red Light Panels? Depends Who You Ask.
Is Flicker Dangerous? We have covered the topic of flicker before but never emphasized the dangers and the history of flicker. And we will drive deeper into the specific relevance for red light therapy panels.
Electronic Flicker is usually an invisible modulation of brightness or intensity. It is invisible because it usually cycles at 100 Hz or 120 Hz (depending on region), which is faster than the human eye can perceive, and our brain stitches the light together in what is called "critical flicker fusion" – so it appears continuous and steady.
Since the invention of the AC (alternating current) power grid and artificial lighting, flicker has been a persistent part of the modern lifestyle – even if we can’t see it, it is there. There is a long history of flicker causing headaches, triggering migraines, causing eyestrain, anxiety, or even triggering seizures in sensitive people.
LED Red light panels are no different, if not more important to be designed free of flicker. They should be at least compliant with the minimum flicker safety standards established by the IEEE and EU.  
In some ways flicker is being mitigated in the modern world with high-quality LEDs and computer monitors. Governments and professional industry societies are setting and enforcing new mandates to eliminate flicker from modern lighting.
But new forms of “flicker-like” distress will come from social-media overuse and Virtual Reality (VR) – given a new syndrome name called Cyber Sickness.
We address some common rhetoric used by high-flicker brands and flicker-deniers with facts, studies, industry standards, and calling them out on their bluffs.
Can invisible flicker be dangerous?
Unfortunately, we still routinely attacked by people who don't want to "believe" that flicker is a problem, despite the overwhelming evidence and industry standards. I suppose they need to “see” flicker and feel the same distress that I feel in order to believe it.
As indicated by this thorough article on flicker on AlexFergus.com - Although flicker is an invisible stressor to the eyes and brain, but it doesn't get as much limelight as other invisible health risks such as EMFs, Pollution, bacteria, viruses, pesticides, etc...
Lets start with a quote from a recent 2017 study that summarizes our point:
“Aversive flicker can also be produced by conventional lighting. For example, lamps that flicker with frequencies of 100 Hz or 120 Hz may appear steady and continuous because the flicker is above the critical flicker fusion threshold, but may nevertheless contribute to headaches and migraine (Poplawski and Miller, 2013; Wilkins et al., 1989).” 
As Alex measured in his massive review, all of the Red Light Panels he measured flickered at 100 Hz (because his AC power grid is 50 Hz, if he took the same measurements in the USA, they would flicker at 120 Hz).
Starting to see the connection? More on this later.
We aren’t the only ones talking about flicker:
Why else would Alex Fergus put Flicker as one of the top criteria to rank red light therapy panels? Because it is a significant consideration for the therapy, a safety risk, and perhaps a sign of high-quality to be low-flicker?
Health experts and influencers such as Alexander Wulch, Dr. Mercola, Jack Kruse, and Ben Greenfield often vainly try to avoid flicker by downgrading to incandescent bulbs (but if they read my posts, they would know that high quality LEDs actually have LESS flicker than incandescent bulbs).  
So if you don’t want to hear it from me, feel free to visit those other health influencer’s pages.
Rational rhetoric versus facts and data:
Unfortunately, when we are attacked on the topic our assailants only use lousy rhetoric, strawman arguments, and sloppy logic. It is never supported by facts or studies, since there are no studies that would conclude that high flicker is "safe."
One flicker-denier claims to be an electrical engineer, yet ignores industry standards set by the IEEE (Institute of Electrical and Electronics Engineers) on the hazards and safety requirements for lighting flicker. This type of convenient omission seems common for this character, but once he realizes this embarrassing oversight – it is likely he will change his narrative, take these references and sources, and pretend he had it correct all along (again).
It is often a thankless job to try to steer this industry in the right direction, even though we seem to be a source of great “inspiration” for people.
Photobiomodulation expert, or Flicker expert?
A popular quote from Joovv interviewing Dr. Hamblin indicates that flicker probably isn't a problem and might be kind of like pulsing. While we love Dr. Hamblin's work, we don't see how an offhand remark without any study reference or clinical trial is valid data – trying to ignore the fact that he is a paid advisor for Joovv.
Advice to the Industry from a Flicker expert.
We reached out to Dr. Jennifer Veitch – a leading expert and researcher on flicker and healthy lighting.
I emailed her about our concerns of people using potentially high-flicker red light therapy products – especially exposing the face and eyes to the flicker. This was her reply:
Dear Mr. LaTour,
You definitely need to minimize temporal light modulation of your sources if you are trying for a therapeutic effect without causing unintended consequences. Red light in particular can be problematic for people with photosensitive epilepsy. I suggest you get a copy of this document and follow its guidance. It’s probably not free, but the cost of buying it could save you a lot of liability:
Harding, G., Wilkins, A. J., Erba, G., Barkley, G. L., & Fisher, R. S. (2005). Photic- and pattern-induced seizures: Expert consensus of the Epilepsy Foundation of America Working Group. Epilepsia, 46(9), 1423-1425. https://doi.org/10.1111/j.1528-1167.2005.31305.x
Dr. Veitch makes excellent points about the risks of deep-red flicker, which specifically has been researched and identified as a trigger for seizures.
As well we will talk about the expensive liability for potentially causing harm to people, and how legitimate brands are mitigating those risks.
A clear divide in marketing flicker in Red Light Panels:
So we see this split of logic among the red light panel brands.
- Companies selling low-flicker panels will educate people about how flicker is possibly detrimental to their health and reduce the effectiveness of red light therapy.
- Companies selling high-flicker panels will say that flicker is a non-issue and is potentially a benefit because it is kind of like pulsing.
Hence the subtitle for this post - "It depends who you ask."
Unfortunately according to my competitors and antagonists; the truth and facts don't matter - only convincing logic and rhetoric that serves their agenda.
This quote from the show Brooklyn Nine-Nine highlights the dangers of using convincing logic without checking the facts.
Let's take another look at the recent standards and science in the flicker industry today, and see how it is relevant to red light therapy.
Why flicker was so dangerous in the past:
The history on the health hazards on light flicker is well documented in many lighting industry articles.
Here is a short overview to jog our memory:
- Since the mass production of movies and TVs starting in the early 1900’s was identified the issue of screen flicker and photosensitive epilepsy.
- The roll-out of fluorescent lighting in the workplace in the 1980’s was when office workers started complaining of migraines and headaches.
- The original introduction LED was worse, with potentially higher flicker % due to the LED’s fast responsiveness and PWM dimming.
- Computer monitors have been a source of flicker distress, especially ones using PWM dimming or flickering fluorescent or LED backlighting.
Old Televisions would utilize our critical flicker fusion by "scanning" or "rastering" the images rapidly. Often to deleterious effects to sensitive people.
So anyone with a memory that can extend beyond the 2000’s might be aware of this interesting history of lighting flicker evolution.
Adapted for “natural” flicker:
Humans and animals are quite adaptable and resilient, which is why we don’t drop dead when we encounter new challenges or man-made forces.
Although we mostly evolved under the continuous light from the sun and we often want to emulate nature to promote holistic health, there are certainly some adaptations we have for coping with flicker.
Sunlight is continuous and non-flickering. We often want to simulate nature with our health devices.
What are some “natural” sources of flicker?
- Flickering in candles and campfire
- Light shimmering and shifting from the waves in the water
- Shadows shifting as the wind blows the leaves and the trees
- Blinking your eyes quickly
- Jogging or driving and seeing the light shifting through the trees
- Striped lines and certain geometric patterns
The zebra's camouflage seems to fail against their natural surroundings, but their strips are exploiting the eye's natural weakness to flicker. Predators may become confused and unable single out a striped prey, especially in motion and in dense herds. 
So we have some natural capacity to cope with flicker, but these forms of “flicker” are generally much slower and with less contrast than the “electronic flicker” or artificial flicker that we will be talking about.
If seizures are such a high risk, where are there any recent reports of it?
I always start with the famous “Pokemon Incident” since I am always surprised when so-called experts in light therapy aren’t aware of this historic event that helped define flicker safety regulations for the world (more on that later). 
Maybe the Pokemon incident is old news, where are the recent incidents and reports?
Right under your nose. I suppose people making this rhetoric don’t bother with a quick google-search on recent reports and studies. A basic fact-check before trolling people would be proper online etiquette in this age of misinformation.
The December 2020 article below tells us that a professional video game journalist suffered a seizure while playing a new video game before it was released to the public. The video game company was notified, and reprogrammed the flicker for the game before it was released to prevent other people from being affected.
A 2019 social medial incident occurred where attackers sent strobing images via social media to the epilepsy foundation. This is fascinating because these attackers KNEW exactly the type of flicker modulations that can trigger seizures. If we know what DOES cause seizures, then we should know what types of flicker to avoid to keep us safe.
A 2019 headline tells us a videogamer suffered a seizure while playing, and luckily his friend online called the ambulance for him.
In 2019, Miley Cyrus posted a promotional video on social media with fast flashes, which many of her followers complained of possible migraine and seizure triggers and petitioned her to take it down.
In 2017, a reporter with epilepsy was sent flickering images on twitter and reportedly suffered a seizure.
In a 2008 and 1993 articles we see lawsuits against videogame companies for causing seizures.
So we have 7 reports of flicker distress and seizures in recent history on modern screens and media. It is important to note that these articles help raise awareness, and we see that many entertainment companies are actively avoiding creating content that can cause seizures. At the very least many TV Shows, Cartoons, Movies, and Video Games have a seizure warning for liability reasons. Which they often learn the hard way when they suffer financial losses from a lawsuit.
But how many people are actually affected?
My naysayers seem to imply that photosensitive epilepsy is an insignificant amount of the population.
First if all, this is horrible rhetoric! If there is even a small percentage of people at risk for adverse reactions, it would be irresponsible and negligent for companies to produce products or content that could harm them. This is what Dr. Veitch was referring to with liability, after all.
Lets look at the actual data and statistics, since they are easily obtainable.
According to the CDC, 3.4 million (~1.2% of the population) of people have diagnosed epilepsy.
According to the epilepsy foundation, 3% of the epilepsy population are triggered by flicker.
Well that is only 0.03% (yes, 3 hundredths of a percentage) of the total US population with photosensitive epilepsy, or about 100,000 people in the USA.
Another document says that 1 in 4000 individuals have photosensitive epilepsy. About 0.025% of the population would be at risk. 
Someone who is inconsiderate of public health might say these are inconsequential numbers. Perhaps they are willing to gamble with people’s health and promote high-flicker products to save a couple bucks in manufacturing.
We will see later on that legitimate brands are taking these numbers very seriously. Even if red light panel brands are not.
Studies tell us:
That >60% of photosensitive epilepsy cases are discovered while watching TV. 
The Smithsonian magazine online shares: “As the Epilepsy Foundation writes, many people don’t even realize that they have epilepsy until a flashing light or image triggers a seizure.”
Without proper education or awareness, people could “learn the hard way” if they have photosensitive epilepsy while watching TV or under flickering lights.
The Science of Flicker? Show me the study!
Since these historic incidents like the Pokemon Incident and workplace complaints, there are thousands of studies on understanding how flicker affects our eyes, brain, and health. As well as investigations by top institutions for flicker safety.
We have already referenced several peer-reviewed studies and official industry standards.
An article published in 2020 by the University of Cambridge article noted a rapidly increasing rate of scientific publications about flicker. 
There are thousands of studies on light flicker because it is so fascinating and a very relevant part of health and biology. Flicker is nearly its own category of research like how Photobiomodulation is.
The Less Obvious Effects of Flicker
We always emphasize seizures since that is an obvious effect of flicker and flashing light.
Unfortunately, in this day and age, problems need to be very obvious and affecting their personal lifestyle for people to take it seriously.
Many people won't believe that climate change is a problem until it starts to personally affect them. The same way it seems many people don't "believe" flicker is a problem if they never experienced distress. Photo by Jeffrey Czum from Pexels
Even people suffering from “sick building syndrome” in the 1980’s couldn’t isolate flicker as one of the causes:
“It was difficult to believe that there could be biological health effects when no flicker features were visible at all, especially with literature expounding the fact that the retinal cell was not able to follow that flicker frequency.” 
Technically, the highest-risk region for triggering seizures is between 3 Hz to 70 Hz, which most red light panels operate at 100 Hz and 120Hz. So our detractors could minimize the risk and say it is a non-issue (I personally wouldn’t gamble with people’s health, but let’s go with it for the sake of argument).
Now we will talk more about some of the “less obvious” symptoms and triggers of flicker. Which according to one paper is defined as:
“The less obvious biological effects occur: 1) from flicker that is invisible 2) after exposure of several minutes. Invisible flicker health effects have been reported to include headaches and eye-strain.” 
How long for we use red light therapy panels? At least several minutes? Lets keep that in mind.
Migraines and Headaches: More or Less Obvious Symptoms
Lets run through some numbers again.
According to the CDC, 15.3% of Americans aged 18 years or older reported a migrane or severe headache in the previous 3 months.
One study on environmental migraine triggers states:
“Commonly reported migraine triggers in the indoor environment include bright lights, fluorescent lights, glare, flicker (eg, computer screen, driving along a tree-lined street), neon lights, and busy visual patterns. In the office environment, fluorescent lighting and flicker from the computer screen are often cited. Working at the computer screen precipitated headaches in 14.5% and aggravated it in 31.3% in one case–control study of chronic headache patients.”
So lets say of the 15.3% of Americans that report migraines, 14.5% of them are triggered by working at a computer screen. So presumably we could expect about 2.2% of the total population gets migraines triggered by flicker. I would say that is pretty big!
Modern Flicker Distress: Cyber Sickness and Visual Vertigo:
We established that a small percentage (but significant) of the total population suffers from photosensitive epilepsy and light-induced migraines related to flicker, so these examples might not seem relatable to the average person.
Although I would argue that we need to design products that are safe even for the most vulnerable and sensitive populations, especially health devices like red light therapy.
So we need to look for even more “subtle” or less-obvious signs of flicker affecting us.
Perhaps modern people can relate to what is being called Cyber Sickness. Essentially it is the common symptoms of eyestrain, headaches, dizziness, vertigo, tiredness, or disorientation experienced after scrolling on digital media, long-term usage of screens, or with Virtual Reality (VR).
You might be scrolling quickly though your Instagram or reading scrolling text quickly – for long periods of time. Then when you finally look up or away, it takes some time to get re-oriented and focus your eyes.
Estimates say that 50-80% of people will experience “cyber sickness” on modern screens.
As images and text scroll past quickly, this creates a fast moving modulation of colors, contrast, brightness, and geometries. When this “scrolling” isn’t paired with natural movement, it becomes disorienting like motion-sickness.
One article likened it to the vertigo experienced by helicopter pilots, since the fast, nearly invisible rotation of the blades leads to a kind of flicker distress and confusion. This effect is also documented by the IEEE on flicker.
A quick Pubmed search on Cybersickness yields 91 results! It is clearly going to be a new form of study for flicker-like distress in the modern era.
One April 2021 survey study defines Visually Induced Motion Sickness as:
“VIMS is a common side-effect when watching dynamic visual content from various sources, such as virtual reality, movie theaters, or smartphones.“
Once again, this is a BRAND NEW, modern study that investigated nausea, headache, dizziness, fatigue, and eyestrain in visual media settings (also the most common symptoms defined by the IEEE caused by flicker). The most prominent being simply eyestrain.
I can only assume that the flicker-deniers are suffering from too much eyestrain and malaise from their cyber-sickness-inducing screens to do any deep research on this topic.
Quick Summary: Where are all of people suffering from flicker and screens?
Just to wrap-up this reply to common rhetoric, we have:
- 025-0.03% of people with photosensitive epilepsy
- 2% of people can get migranes or headaches from flicker and screens
- 50-80% of people will experience “cyber sickness” including eyestrain, and other subtle distress like dizziness, fatigue, headaches while using screens, tv, movies, monitors, video games, or AR.
Yes, and still mountains of peer-reviewed research on flicker and cyber sickness – occasional news reports, and publications from the lighting industry and governmental agencies.
Major brands are still adding flicker and seizure disclaimers:
A popular brand-new 2021 TV show like Invincible includes a seizure warning display!
Why would Amazon offer this disclaimer that could possibly deter viewers from watching this fabulous show (mature audiences only, please)? Unless they knew the risks and liabilities for causing seizures would be very expensive.
Here is another disclaimer from Walt Disney World, 2021!
Why, in the year 2021, are Amazon and Disney still adding disclaimers to their content, if my antagonists are pretending the flicker isn’t an issue?
Well, they probably looked at the risks and liabilities for causing a seizure and decided that they needed financial protection if there is an issue. Remember that 1 in 4000 people could be triggered, and if Amazon and Disney expect to have millions of viewers, you will bet that they are taking the correct precautions.
Perhaps the high-flicker red light panel brands should take note of this and add their own disclaimers.
Regulations and Standards for the modern era.
Thanks to the wealth of data on the health effects of flicker, and knowing the science on how to avoid harmful flicker – modern lighting has vastly improved over the years!
Perhaps our children can grow up in a flicker-free world, and flicker will become a long-forgotten myth of a primitive technological past.
- Fluorescent lighting adopted high-frequency ballasts to mitigate flicker distress. 
- LED lighting uses higher-quality drivers to eliminate flicker. 
- IEEE guidelines impose strict criteria for flicker safety. 
- The European Union is implementing stronger flicker regulations. 
- Guidelines are highlighted for media makers to avoid triggering flicker distress. 
- Disclaimers are still being used in media.
- Low Flicker computer monitors are being marketed.
- Low Flicker dimming apps are available.
- Low Flicker light bulbs are being marketed.
- Low cost flicker meters are commercially available.
Philips is even advertising no flicker lighting at the hardware store!
So while I am being belligerently attacked about flicker, behind the scenes these organizations and companies are keeping us safe from flicker.
2020: The End of an Era of Flicker?
A 2020 article from the University of Cambridge titled “A Long Overdue End to Flicker: The 2020 EU Lighting Efficiency Regulation” does an impressive job covering the history of flicker, human health issues, and science and regulations.
They explain the meaning of the new EU Regulation that it is to impose that LEDs are always lower flicker than incandescent bulbs.
Which we know this is a "bare minimum" standard of regulation, that LEDs can actually perform much better than incandescent, so we shouldn't just settle for accepting the bare-minimum standard when we can easily exceed it.
But this is a huge turning-point in flicker requirements for the entire world!
The Cambridge article emphasizes that the UK will also need to comply if they want to sell lights to the EU.
This also means that LED Red Light Therapy panels that want to sell, distribute, or import to the EU will need to be compliant to the new flicker regulations!
Is Flicker an issue with Red Light Therapy Panels?
The original "red light panels" that recently became popular in 2016 were actually retrofitted grow lights (hint, this is also why companies mistakenly used inaccurate Solar Power meters and PAR meters – they might be OK for photosynthesis, but are irrelevant for humans and photobiomodulation).
Here's the thing about plants, they don't complain if they experience high flicker. Even though they, like humans, evolved under a continuous light source such as the sun.
Reducing flicker in an LED panel is rather easy, it takes a bit of extra design work and components in the AC/DC driver to reduce the “ripple” voltage that causes the lights to flicker.
But for cheap plant grow lights, why bother? They can save the money and effort.
I asked one Alibaba supplier the price difference for power drivers for their standard (high flicker) drivers, or low-flicker drivers. It is only $5 extra! Let’s say there are 5 drivers in a body-light, so it would only cost $25 extra per panel!
Well, when companies started retrofitting grow lights with Red and NIR LEDs, they forgot to upgrade the drivers to low-flicker drivers. Like using solar power meters to measure intensity, they were likely ignorant and negligent in the beginning.
We have measured an Original Joovv (Gen 1) at 31% flicker, Gen 2 Joovv at 10% flicker, SGrow VIG1000 at 62% flicker, and Alex Fergus had measured PlatinumLED at 42% flicker and MitoRed at 71% flicker.
So we know Red Light Panels flicker, so what? Is there any risk?
All of these are in the "High Risk" zone defined by the IEEE (maximum of 10% flicker at 120Hz). 
Add to it, Dr. Veiche and the IEEE specifically points out that “Deep Red” flicker is particularly dangerous trigger. This was identified in EEG studies that photosensitive epilepsy brains are highly responsive to deep red as a seizure trigger.
So we have the perfect storm of:
- large high-intensity flickering lights
- aiming at the face and eyes covering the entire field of view
- used for at least several minutes at a time
- with the most triggering color of deep red 
All of these risk factors are amplified in “high-risk” groups with pre-existing photosensitivity, seizure history, migraines, stress or anxiety disorders, children, or sleep-deprived people.
Which, for a health product like red light therapy – people are usually trying to improve their sleep and anxiety, not potentially exacerbate it.
Is Flicker Like Pulsing?
Most PBM studies, unless otherwise noted, use what is called Continuous Wave (CW), meaning there is no flicker or pulsation of the light for the therapy.
Now many studies do indicate that pulsing (PW) produces a superior result compared to Continuous Wave. However, the context is that most studies purposely use higher peak intensity with the pulsed wave to offset the loss of dosage by the duty cycle.
If companies are going to claim flicker as a "benefit" similar to pulsing, then they better take it seriously and get 3rd party measurements for all of their so-called pulsing parameters.
Parameters for pulsing include:
- Peak Intensity
- Average Intensity
- % modulation of intensity
- Duty Cycle
- Hertz (Hz) of the pulse
Flicker, like pulsing, is a rapid modulation of intensity. This means we need to quantify the "highs" and the "lows" to re-calculate the average intensity.
Since most companies are too busy falsifying intensity claims with cheap solar power meters, I doubt they would provide you with such advanced parameters. So once again they are caught using gimmicky rhetoric and can’t follow up with data.
Previously mentioned in our pulsing blog, you should be skeptical of pulsed light claims to begin with. Most researchers would note that pulsing or flicker actually REDUCES the average intensity and dose delivered compared to continuous wave.
Often the companies pushing high intensity panels are also claiming that their flicker is a non-issue - but these are contradictory narratives if we look at the true dose.
Another Expert Opinion?
When we were reaching out to 3rd party labs for intensity measurements, one of them replied with this suggestion:
“One other thing we will do is look at the temporal aspects. This is because as you know far too many LED sources flicker, and this can create a rift between some measurement instruments and assumed dose. You want to know if your light is running a higher peak power, but lower duty cycle, etc.. especially for eye safety.”
Which I was very happy to get this response, because I hadn’t even asked about flicker yet! Finally someone else out there understands the obvious – that flickering will affect your dosage calculations unless you measure it properly.
Although flicker isn't a popular or trendy health issue, it has been a real part of human existence since the invention of the artificial light bulb.
There are numerous reports and studies about the hazards and effects of flicker on humans including headaches, migraine, and neurological issues like seizure triggers.
It is essentially common-knowledge that invisible flicker at 100Hz or 120Hz (the most common flicker frequencies for lighting and red light panels), can cause distress.
Here is the statement from the 2020 University of Cambridge article:
“Exposure to light flickering at 100Hz has been linked to eyestrain, headaches and migraines, even though this rate of flicker is above the human perceptual flicker-fusion frequency of around 60 Hz.” 
These adverse effects and studies have increased significantly since the invention of fluorescent lighting, LED lighting, TV and monitors, and video media. And there are many examples in recent history of flicker issues and concerns.
Perhaps now, in 2021 and beyond – we expect that there will be less flicker distress reported. Because industry guidelines, government guidelines, media guidelines, quality improvements of monitors and lighting, and general awareness have encouraged creators and manufacturers to make safer products and content.
Some retaliatory blogs are trying to “debunk” that flicker is a non-issue while recklessly ignoring industry standards for safety.
And aside from the mountains of research and evidence that flicker is a very relevant problem for red light therapy, we have two direct recommendations from experts:
- The expensive liability risks of exposing people to flickering red lights.
- The temporal modulation of intensity (flicker) will affect your dosing calculations.
Unfortunately, many red light panel brands still need to reduce their flicker and improve the driver quality. It doesn’t cost much, but they seem to have no incentive to improve if their customers don’t demand low-flicker technology.
Pretty soon, Red Light Panel companies won’t have a choice. There won’t be any debate. They need to reduce flicker in their panels to:
- Reduce liability for causing seizures, migraines, or cyber-sickness-type symptoms.
- Comply with EU directives and industry standards.
- Be competitive in the health industry.
Until then, be careful who you ask about flicker. They may use convincing logic and rhetoric, but conveniently overlook decades of health issues, studies, and industry standards.
Sanae Yoshimoto, Jesel Garcia, Fang Jiang, Arnold J. Wilkins, Tatsuto Takeuchi, Michael A. Webster, Visual discomfort and flicker, Vision Research, Volume 138, 2017, Pages 18-28,
Weinold, M. (2020). A Long Overdue End to Flicker: The 2020 EU Lighting Efficiency Regulations. Cambridge Journal of Science and Policy, 1(1).
Regulations: What Next?
First published: 07 January 2004
LpR Article | Research | Aug 11, 2016
Flicker Beyond Perception Limits - A Summary of Lesser Known Research Results
Ben Greenfield Energy Hacks Incandescent
Energy "Hacks": Sabbath Ramblings with Ben Greenfield (bengreenfieldfitness.com)
 Mercola Flicker
Jack Kruse, The Flicker Effect of Light
Hughes, A.E., Troscianko, J. & Stevens, M. Motion dazzle and the effects of target patterning on capture success. BMC Evol Biol 14, 201 (2014). https://doi.org/10.1186/s12862-014-0201-4