100Hz flicker in lighting is hazardous to humans?

[Flyback]

Hello,
Please can we de-nonsense the “100Hz flicker problem” in lighting?

The web is full of conflicting stories about whether or not 100Hz flicker is actually harmful to humans.

I believe that 100Hz flicker in lighting is no problem whatsoever…..i lived under the old magnetic ballast fluorescent lighting for decades…and had no problem with its 100Hz flicker. Also, driving down motorways with sodium vapour lamp streetlighting which flickers at 100Hz, caused me no problem whatsoever…..and no problem to other drivers either.

Headaches in today’s world are more likely to be caused by Hangovers, too much caffeine, too much sugar, too little exercise, too little sleep due to watching Netflix all night, etc etc…..

The 100Hz flicker problem in lighting is simply a nonsense story pervaded by large electronics corporations so that they can sell their integrated circuits and lamps which get rid of this 100Hz flicker.

Also, most of the large electronics corporations have decided to volume manufacture LED power supplies with large-ish electrolytic capacitor banks, (eg after the PFC stage) which makes them cheaper and easier to design……..and means the 100Hz flicker is easily avoided…….having committed their resources to this in vast quantity, they then are looking to create nonsense stories about smaller manufacturers who make lamps which do flicker at 100Hz….in other words, yet again, all we are seeing, is the large globalist corporations lobbying Governments so as to increase their profits and destroy their smaller rivals.

Surely you agree?

There is not one single piece of conclusive evidence to state that 100Hz lighting flicker is actually a problem……..nonsense?

**broken link removed**

 

[gophert]

I'm happy to be living in a region where lights flicker at the much safer frequency of 120Hz.

 

[audioguru]

3% to 5% of the 50 million people in the world have photosensitivity causing epilepsy seizures, "Flickering or "high frequency" light sources are often triggering for those with photosensitive epilepsy. Frequencies of about 5-30 flashes per second are more likely to induce a light-triggered seizure."

 

[ronsimpson]

“100Hz flicker problem” .............. fluorescent lighting

Old bulbs have a problem that in one direction they produce more light than in the other. They (using Flyback's example) produces 100hz and 50hz noise.
In the center of your vision you can not see 50hz noise. At the edge of your vision you can. Some people, we tested, can see above 60hz in the edge of their vision. That is why we pushed CRT monitor up to 75 then later 90hz.

light-triggered

My wife has headache problems when using sealing fans with lights. Back with "CPM" and later "DOS" computer that have white text on a black background she was fine. If I changed to black text on white background she had problems. With Windows 3 I had to push the vertical frequency up on the CRT monitors. (or switch to a dark background with white text)

Surely you agree?

Saying that no one has "power line flicker" problems is like my neighbor that says every one likes the smell of roses. She splashes on "rose water" that causes me to sneeze and get headaches.

 

[gary350]

The human eye can not see flicker above a certain Hz, movie film flickers at 60 Hz. TV flickers too, not sure what Hz is for digital TV? I never heard of anyone having epilepsy seizures in movie theaters because of Flickering or at home watching TV. Your eye can not see moving objects police are trained to glance at a license plate then close your eyes and read the image stored in your brain. I read where fluorescent lights flicker but most people can not see it that sometimes causes some people to have epilepsy seizures.

 

[DrG]

IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers

 

[gophert]

There is not one single piece of conclusive evidence to state that 100Hz lighting flicker is actually a problem……..nonsense?

The human eye can sense way above 60Hz - it all depends on how you look at the flashing object.
For example, GM has taken to using PWM modulation on their taillight/brake light assembly on Cadillac and Corvettes with LED rear lighting.

GM claims they are pulsing the lights way above human perception but that is only when looking directly at the light. If you are behind a GM car and scan left and right (rotate head PLUS change directly of eye scan at the same time) an high scan rate across the field of vision can be achieved (degrees per second). Thus even GMs 90 pulses per second of high-intensity LEDs are easily discerned through persistence of vision by a distracting chain of red taillight across the eye).

Minimum PWM frequency selectiunder review at several standards-setting committees in SAE and DOT.

 

[Nigel Goodwin]

The human eye can not see flicker above a certain Hz, movie film flickers at 60 Hz.

Not at all, movie film is 24 frames per second - hence the problems converting films to TV - particularly in the US, it's not bad here as it's already very close.

TV flickers too, not sure what Hz is for digital TV?

Flat screen TV's don't work in the same way as CRT's, so don't really flicker - but the signal is essentially the same, 50Hz over here, and 60Hz in the USA.

Most sets process the picture to supposedly improve it, although I'm not really sure it does, so a 100/120Hz set would generate an extra picture in-between the two actual frames of the video. This obviously takes a LOT of processing power, and is probably the most important difference between cheap sets and good quality ones - the same system also scales the picture to fit the screen. There are also higher frame rate sets, which generate extra pictures again, and again, between the original frames - my Sony Android set is apparently 800Hz.

The old Plasma sets weren't capable of more than 100Hz, as is obvious by the way they work - although the marketing guys invented a totally fictitious measurement that was intended to fool people in to believing that they had faster frame rates equal to LCD.

 

[DrG]

/-- snip--/ I never heard of anyone having epilepsy seizures in movie theaters because of Flickering or at home watching TV. /-snip-/

**broken link removed**

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.532.7063&rep=rep1&type=pdf

Now you have

 

[JimB]

I can think of two instances where I have been "affected" by lighting.

25+ years ago in a hotel, one of the restaurant/lounge areas was illuminated by the (then) new compact florescent lamps.
I was glad to eat up and get out of that room, it felt quite unpleasant.

30+ years ago in a factory, one room had several light fittings of the type where three or four short (about 2 foot long) florescent tubes were grouped together.
This room gave me a headache and hurt my eyes. This may have even given me a touch of migraine, I felt awful that week at that place.

So, other than those two instances, which may or may not have been directly attributable to the lighting, no problems.

Surely you agree?

I am not sure that I do.

JimB

 

[MaxHeadRoom78]

I recall back in the 50's in the UK when fluorescent lighting came out and one problem that soon appeared was when they were installed in machine shops, the barely visible flicker on 50hz caused a strobe effect on machine spindles, often the operator would mistakenly take the spindle as stopped when changing a tool and lose fingers or a hand.
The remedy was to put the lighting across 3 phases in workplaces of this nature.
Max.

 

[gophert]

I recall back in the 50's in the UK when fluorescent lighting came out and one problem that soon appeared was when they were installed in machine shops, the barely visible flicker on 50hz caused a strobe effect on machine spindles, often the operator would mistakenly take the spindle as stopped when changing a tool and lose fingers or a hand.
The remedy was to put the lighting across 3 phases in workplaces of this nature.
Max.

We had a similar effect years ago with the blades of a ceiling fan hung below a light fixture making a low-tech strobe light. Luckily nobody was hurt but it was an interesting effect.

 

[gary350]

My work shop has 17 florescent lights each with 2 bulbs. On a cold winter day before heat in the shop is turned on 34 light bulbs are flashing like strobe lights it drives my eye crazy but it never causes me to have epilepsy seizures. I fire up the wood stove and it is 75 degrees in the shop in about 20 minutes all the florescent lights stop flashing when it gets warmer. The trick to getting lightning fast heat from a wood stove is run the stove pipe all the way around the whole 24'x30' room 92 feet of stove pipe. Pipe at the stove is about 800 degrees and pipe where it goes out the wall is about 80 degrees. There is 4 ft of pipe that goes straight up form the stove and 2 ft that goes out the wall so that makes a total of 98 ft of 6" diameter stove pipe that dissipated heat into the workshop. Once the workshop is hot it takes a tiny fire to keep it warm.

 

[ronsimpson]

movie film is 24 frames per second

Updating a picture 24 or 18 times a second does not cause low frequency flicker.
Example: If you could keep the lamp on 95% of the time and off for 5% to advance the film your eye will like thins.
Example: Some projectors flashed the same frame 2, 3, or 4 times per frame to not have flicker. Some systems have 24 frames/second but 72hz flicker.

 

[ChrisP58]

My work shop has 17 florescent lights each with 2 bulbs. On a cold winter day before heat in the shop is turned on 34 light bulbs are flashing like strobe lights it drives my eye crazy but it never causes me to have epilepsy seizures.
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Do you otherwise get epileptic seizures?

The issue with flashing lights is not that they cause non epileptics to have seizures. It's that they can trigger seizures in those who already get them. And even then, I doubt that it affects all epileptics the same.

 

[carbonzit]

Interesting question. Regarding whether or not we can perceive such flickering, I've noticed an interesting thing with LED taillights on newer cars. I don't notice any flicker in them if I look straight at them, but if I scan them--move my eyes rapidly across them--I can definitely see "dashes" of light, indicating low-frequency flashing. Dunno of this affects anyone adversely, but I wouldn't be surprised if it did.

What I have a problem with is people who claim that the "flicker" in them newfangled light bulbs (CFLs and LEDs) affects them. Those bulbs do pulsate,, but the rate is way up in the multiples of kHz, which I don't think anyone can actually sense.

 

[carbonzit]

I can think of two instances where I have been "affected" by lighting.

25+ years ago in a hotel, one of the restaurant/lounge areas was illuminated by the (then) new compact florescent lamps.
I was glad to eat up and get out of that room, it felt quite unpleasant.

30+ years ago in a factory, one room had several light fittings of the type where three or four short (about 2 foot long) florescent tubes were grouped together.
This room gave me a headache and hurt my eyes. This may have even given me a touch of migraine, I felt awful that week at that place.

I don't doubt you at all. But was it the light flickering that bothered you, or was it the color of the light? In the factory, I'd guess that they used "cool white" (or "daylight") lamps, probably at least 4000k, which are quite blue in color. I don't like those either.

 

[OlPhart]

I'll add nobody has mentioned the beat frequency of a fluorescent at 120Hz of ambient light on a monitor at 60-75Hz.
In the early 80s, I put a hood over my monitor to keep headaches at bay.

I recommend cool white for high visual acuity in shop floor areas by blue content, warm white for office areas to lower stress by red content.

Previous post of white text / black back ok, But black text over white back bad is due to amount of area "flickering" that they're concentrating on.
I sympathize... <<<)))

 

[Diver300]

CRT monitors dim a lot between frames. Take a high-speed photo of a CRT monitor and a lot of the image will be dark.

An LCD monitor will basically stay at constant brightness between frames, so even if it is updating slowly, there's no flicker. A moving image on screen will be moving in a series of jumps, so the slower the frame rate, the larger the jumps.

Sensitivity to flicker varies enormously between people. I appear to be very sensitive to it, and I find the 100 Hz lighting on cars highly irritating, even though I can't see it flickering unless there is movement. Of course, at night, there is a lot of contrast which makes it worse, and the flicker becomes visible as I look away or towards a 100 Hz light, and in normal driving, there's a lot of looking at different things.

The 100 Hz flicker on car lights is often worse than the 100 Hz flicker on some 50 Hz lightbulbs because the duty cycle is different. Some car tail lights are only on for 10% of the time, so there are 9 ms gaps in the lighting. Some 50 Hz lightbulbs dim as the voltage reduces and and so they are on for the majority of the time and the actual dark period is probably only about 2 ms.

There are many ways that LED lightbulb circuits are arranged, and one method that I have seen used is a series capacitor as a current limiting device, followed by a bridge rectifier, the smoothing capacitor and the LEDs. On several of these the smoothing capacitor is far too small so it does little to reduce flicker, and I have virtually eliminated flicker by adding a significantly larger capacitor.

Flicker can be photographed by deliberately moving the camera during the exposure so that the image becomes a series of dots, like this:- http://www.malin.me.uk/vwflashsm.jpg That shows 100 Hz car lighting as dots, 50 Hz street lighting (so modulated at 100 Hz) as the orange strip with gaps, while a steady light, in this case an incandescent one, is a uniform strip. The photo gives an idea of what I see as I move my eyes.

I've been able to detect higher frequencies. I've used the moving camera technique to estimate the flashing frequency of one set of car lights at about 2 kHz. I had noticed the flicker with the naked eye before taking the photo. Beyond about 500 Hz I don't find the flickering distracting, even though I can see it.

There was TV documentary many years ago where the effect of fluorescent lighting with 100 Hz modulation was measured by experiments on volunteers. Even when the volunteers couldn't say whether there was modulation, when they moved their eyes to look in a different place, they were less accurate when there was lighting modulation, with their eyes often overshooting the correct position at first.

I don't think that 100 Hz lighting is harmful, but I know that it can be intensely irritating to me, even when other people are unable to detect flicker. It seems to me that allowing flicker in lighting systems just because only 5 - 10% of the population can tell the difference is simply bad engineering.

 

[Diver300]

What I have a problem with is people who claim that the "flicker" in them newfangled light bulbs (CFLs and LEDs) affects them. Those bulbs do pulsate,, but the rate is way up in the multiples of kHz, which I don't think anyone can actually sense.

There are lots of electronic design, and those that have SMPS in them will generally be switching at frequencies too high to be visible, but the mains voltage variations can get through on some. Other designs will have a lot of modulation at twice the mains frequency, and I have seen indicator lights that are run at 50 Hz (https://www.electro-tech-online.com/threads/intermittent-leds.147691/#post-1258465)